diff --git a/src/main/scala/org/biodatageeks/sequila/flagStat/FlagStat.scala b/src/main/scala/org/biodatageeks/sequila/flagStat/FlagStat.scala
new file mode 100644
index 00000000..e1c916fc
--- /dev/null
+++ b/src/main/scala/org/biodatageeks/sequila/flagStat/FlagStat.scala
@@ -0,0 +1,165 @@
+package org.biodatageeks.sequila.flagStat
+
+import htsjdk.samtools.SAMRecord
+import org.apache.spark.rdd.RDD
+import org.apache.spark.sql.catalyst.InternalRow
+import org.apache.spark.sql.catalyst.expressions.Attribute
+import org.apache.spark.sql.{DataFrame, Dataset, Row, SparkSession}
+import org.biodatageeks.sequila.datasources.BAM.{BAMFileReader, BAMTableReader}
+import org.seqdoop.hadoop_bam.{BAMBDGInputFormat, CRAMBDGInputFormat}
+import org.slf4j.LoggerFactory
+import org.apache.spark.sql.types.{LongType, StructField, StructType}
+import org.biodatageeks.sequila.datasources.InputDataType
+import org.biodatageeks.sequila.inputformats.BDGAlignInputFormat
+import org.biodatageeks.sequila.pileup.PileupMethods
+import org.biodatageeks.sequila.pileup.conf.Conf
+import org.biodatageeks.sequila.utils.{FileFuncs, TableFuncs}
+
+import scala.collection.mutable.ListBuffer
+
+case class FlagStatRow(
+	RCount: Long,
+	QCFail: Long,
+	DUPES: Long,
+	MAPPED: Long,
+	UNMAPPED: Long,
+	PiSEQ: Long,
+	Read1: Long,
+	Read2: Long,
+	PPaired: Long,
+	WIaMM: Long,
+	Singletons: Long
+);
+
+case class FlagStat(spark:SparkSession) {
+	val Logger = LoggerFactory.getLogger(this.getClass.getCanonicalName);
+
+	def processFile(bamFilePath: String) : DataFrame = {
+		val tableReader = new BAMFileReader[BAMBDGInputFormat](spark, bamFilePath, null);
+		val records = tableReader.readFile
+		processDF(processRows(records))
+	}
+
+	def processRows(records: RDD[SAMRecord]) : RDD[(String, Long)] = {
+		records.mapPartitions((m) => {
+			var RCount = 0L;
+			var QCFail = 0L;
+			var DUPES = 0L;
+			var UNMAPPED = 0L;
+			var MAPPED = 0L;
+			var PiSEQ = 0L;
+			var Read1 = 0L;
+			var Read2 = 0L;
+			var PPaired = 0L;
+			var WIaMM = 0L;
+			var Singletons = 0L;
+
+			while (m.hasNext) {
+				val iter = m.next;
+
+				if (iter.getReadFailsVendorQualityCheckFlag()) {
+					QCFail += 1;
+				}
+				if (iter.getDuplicateReadFlag()) {
+					DUPES += 1;
+				}
+				if (iter.getReadUnmappedFlag()) {
+					UNMAPPED += 1;
+				} else {
+					MAPPED += 1;
+				}
+				if (iter.getReadPairedFlag()) {
+					PiSEQ += 1;
+					if (iter.getSecondOfPairFlag()) {
+						Read2 += 1;
+					} else if(iter.getFirstOfPairFlag()) {
+						Read1 += 1;
+					}
+					if (iter.getProperPairFlag()) {
+						PPaired += 1;
+					}
+					if (!iter.getReadUnmappedFlag() && !iter.getMateUnmappedFlag()) {
+						WIaMM += 1;
+					}
+					if (!iter.getReadUnmappedFlag() && iter.getMateUnmappedFlag()) {
+						Singletons += 1;
+					}
+				}
+				RCount += 1;
+			}
+
+			//Iterator(Row(RCount, QCFail, DUPES, MAPPED, UNMAPPED, PiSEQ, Read1, Read2, PPaired, WIaMM, Singletons))
+			Iterator(
+				("RCount", RCount),
+				("QCFail", QCFail),
+				("DUPES", DUPES),
+				("MAPPED", MAPPED),
+				("UNMAPPED", UNMAPPED),
+				("PiSEQ", PiSEQ),
+				("Read1", Read1),
+				("Read2", Read2),
+				("PPaired", PPaired),
+				("WIaMM", WIaMM),
+				("Singletons", Singletons)
+			)
+		}).reduceByKey((v1, v2) => v1 + v2)
+	}
+	def processDF(rows: RDD[(String, Long)]): DataFrame = {
+		var mapping = rows.collectAsMap();
+		var sequence = new ListBuffer[Long];
+		FlagStat.Schema.fieldNames.foreach(x => {
+			sequence += mapping.get(x).get;
+		})
+		val result = Row.fromSeq(sequence);
+		val rdd = spark.sparkContext.parallelize(Seq(result));
+		spark.createDataFrame(rdd, FlagStat.Schema);
+	}
+
+
+	def handleFlagStat(tableNameOrPath: String, sampleId: String): RDD[(String, Long)] = {
+		if(sampleId != null)
+			Logger.info(s"Calculating flagStat on table: $tableNameOrPath")
+		else
+			Logger.info(s"Calculating flagStat using file: $tableNameOrPath")
+
+		val (records) = {
+			if (sampleId != null) {
+				val metadata = TableFuncs.getTableMetadata(spark, tableNameOrPath)
+				val tableReader = metadata.provider match {
+					case Some(f) if sampleId != null =>
+						if (f == InputDataType.BAMInputDataType)
+							new BAMTableReader[BAMBDGInputFormat](spark, tableNameOrPath, sampleId, "bam", None)
+						else throw new Exception("Only BAM file format is supported.")
+					case None => throw new Exception("Empty file extension - BAM file format is supported..")
+				}
+				tableReader
+					.readFile
+			}
+			else {
+				val fileReader = FileFuncs.getFileExtension(tableNameOrPath) match {
+					case "bam" => new BAMFileReader[BAMBDGInputFormat](spark, tableNameOrPath, None)
+				}
+				fileReader
+					.readFile
+			}
+		}
+
+		processRows(records);
+	}
+}
+
+object FlagStat {
+	val Schema = StructType(Array(
+		StructField("RCount", LongType, false),
+		StructField("QCFail", LongType, false),
+		StructField("DUPES", LongType, false),
+		StructField("MAPPED", LongType, false),
+		StructField("UNMAPPED", LongType, false),
+		StructField("PiSEQ", LongType, false),
+		StructField("Read1", LongType, false),
+		StructField("Read2", LongType, false),
+		StructField("PPaired", LongType, false),
+		StructField("WIaMM", LongType, false),
+		StructField("Singletons", LongType, false)
+	));
+}
\ No newline at end of file
diff --git a/src/main/scala/org/biodatageeks/sequila/flagStat/FlagStatStrategy.scala b/src/main/scala/org/biodatageeks/sequila/flagStat/FlagStatStrategy.scala
new file mode 100644
index 00000000..aa1306d2
--- /dev/null
+++ b/src/main/scala/org/biodatageeks/sequila/flagStat/FlagStatStrategy.scala
@@ -0,0 +1,83 @@
+package org.biodatageeks.sequila.flagStat
+
+import okhttp3.logging.HttpLoggingInterceptor.Logger
+import org.apache.spark.rdd.RDD
+import org.apache.spark.sql.{Encoders, FlagStatTemplate, PileupTemplate, Row, SparkSession, Strategy}
+import org.apache.spark.sql.catalyst.InternalRow
+import org.apache.spark.sql.catalyst.expressions.Attribute
+import org.apache.spark.sql.catalyst.plans.logical.LogicalPlan
+import org.apache.spark.sql.execution.SparkPlan
+import org.apache.spark.sql.execution.command.CreateDataSourceTableAsSelectCommand
+import org.apache.spark.sql.execution.datasources.InsertIntoHadoopFsRelationCommand
+import org.biodatageeks.sequila.datasources.BAM.BDGAlignFileReaderWriter
+import org.biodatageeks.sequila.datasources.InputDataType
+import org.biodatageeks.sequila.inputformats.BDGAlignInputFormat
+import org.apache.spark.sql.catalyst.encoders.{ExpressionEncoder, RowEncoder}
+import org.biodatageeks.sequila.pileup.Pileup
+import org.biodatageeks.sequila.pileup.conf.Conf
+import org.biodatageeks.sequila.pileup.conf.QualityConstants.{DEFAULT_BIN_SIZE, DEFAULT_MAX_QUAL}
+import org.biodatageeks.sequila.utils.{FileFuncs, InternalParams, TableFuncs}
+import org.seqdoop.hadoop_bam.{BAMBDGInputFormat, CRAMBDGInputFormat}
+
+import scala.collection.mutable.ListBuffer
+import scala.reflect.ClassTag
+
+class FlagStatStrategy (spark:SparkSession) extends Strategy with Serializable {
+
+  override def apply(plan: LogicalPlan): Seq[SparkPlan] = {
+    plan match {
+      case CreateDataSourceTableAsSelectCommand(table, mode, query, outputColumnNames) => {
+        table.storage.locationUri match {
+          case None => None
+        }
+        Nil
+      }
+      case InsertIntoHadoopFsRelationCommand(outputPath, staticPartitions, ifPartitionNotExists, partitionColumns, bucketSpec, fileFormat, options, query, mode, catalogTable, fileIndex, outputColumnNames) => {
+        Nil
+      }
+      case FlagStatTemplate(tableNameOrPath, sampleId, output) => {
+        val inputFormat = {
+          if (sampleId != null)
+            TableFuncs.getTableMetadata(spark, tableNameOrPath).provider
+          else if (FileFuncs.getFileExtension(tableNameOrPath) == "bam") Some(InputDataType.BAMInputDataType)
+          else None
+        }
+        inputFormat match {
+          case Some(f) =>
+            if (f == InputDataType.BAMInputDataType)
+              FlagStatPlan[BAMBDGInputFormat](plan, spark, tableNameOrPath, sampleId, output) :: Nil
+            else Nil
+          case None => throw new RuntimeException("Only BAM file format is supported in flagStat function.")
+        }
+      }
+      case _ => Nil
+    }
+  }
+}
+
+object FlagStatPlan extends Serializable {
+
+}
+case class FlagStatPlan [T<:BDGAlignInputFormat](plan:LogicalPlan, spark:SparkSession,
+                                               tableNameOrPath:String,
+                                               sampleId:String,
+                                               output:Seq[Attribute] // ,directOrcWritePath: String = null)(implicit c: ClassTag[T]
+                                               )
+  extends SparkPlan with Serializable  with BDGAlignFileReaderWriter [T]{
+
+  override protected def otherCopyArgs: Seq[AnyRef] = Seq()
+
+  override def children: Seq[SparkPlan] = Nil
+
+  override protected def doExecute(): RDD[InternalRow] = {
+    val fs = new FlagStat(spark);
+    val rows = fs.handleFlagStat(tableNameOrPath, sampleId);
+    val mapping = rows.collectAsMap;
+    val fields = new ListBuffer[Long];
+    FlagStat.Schema.fieldNames.foreach(x => {
+      fields += mapping(x);
+    })
+    val result = InternalRow.fromSeq(fields);
+    spark.sparkContext.parallelize(Seq(result));
+  }
+}
diff --git a/src/main/scala/org/biodatageeks/sequila/flagStat/flagStatDebugger.scala b/src/main/scala/org/biodatageeks/sequila/flagStat/flagStatDebugger.scala
new file mode 100644
index 00000000..b0dd3ba0
--- /dev/null
+++ b/src/main/scala/org/biodatageeks/sequila/flagStat/flagStatDebugger.scala
@@ -0,0 +1,34 @@
+package org.biodatageeks.sequila.flagStat
+
+import org.apache.spark.sql.{DataFrame, SequilaSession, SparkSession}
+import org.apache.spark.storage.StorageLevel
+import org.biodatageeks.sequila.utils.InternalParams
+import org.slf4j.LoggerFactory
+
+object FlagStatDebuggerEntryPoint {
+	val sampleId = "NA12878.proper.wes.md"
+	val bamFilePath: String = s"/Users/mwiewior/research/data/WES/${sampleId}.bam";
+
+
+
+	def main(args: Array[String]): Unit = {
+		performance(bamFilePath, null);
+	}
+
+	def performance(tableNameOrPath: String, sampleId: String): Unit = {
+		System.setSecurityManager(null);
+		val spark = SparkSession
+			.builder()
+			.master("local[4]")
+			.config("spark.driver.memory","8g")
+			.config("spark.biodatageeks.bam.validation", "SILENT")
+			.config("spark.biodatageeks.readAligment.method", "hadoopBAM")
+			.config("spark.biodatageeks.bam.useGKLInflate", "true")
+			.getOrCreate();
+		val ss = SequilaSession(spark);
+		ss.time {
+			ss.flagStat(tableNameOrPath, sampleId).show();
+		}
+		ss.stop()
+	}
+}
\ No newline at end of file
diff --git a/src/main/scala/org/biodatageeks/sequila/utvf/ResolveTableValuedFunctionsSeq.scala b/src/main/scala/org/biodatageeks/sequila/utvf/ResolveTableValuedFunctionsSeq.scala
index 062f6ca6..c81db035 100644
--- a/src/main/scala/org/biodatageeks/sequila/utvf/ResolveTableValuedFunctionsSeq.scala
+++ b/src/main/scala/org/biodatageeks/sequila/utvf/ResolveTableValuedFunctionsSeq.scala
@@ -20,7 +20,6 @@ package org.apache.spark.sql
 
 
 import java.util.Locale
-
 import org.apache.spark.sql.ResolveTableValuedFunctionsSeq.tvf
 import org.apache.spark.sql.catalyst.analysis.{MultiInstanceRelation, TypeCoercion, UnresolvedTableValuedFunction}
 import org.apache.spark.sql.catalyst.expressions.{Alias, Attribute, Expression}
@@ -28,10 +27,10 @@ import org.apache.spark.sql.catalyst.plans.logical._
 import org.apache.spark.sql.catalyst.rules._
 import org.apache.spark.sql.internal.SQLConf
 import org.apache.spark.sql.types.{StructField, _}
+import org.biodatageeks.sequila.flagStat.FlagStat
 import org.biodatageeks.sequila.pileup.conf.QualityConstants
 import org.biodatageeks.sequila.utils.Columns
 
-
 /**
   * Rule that resolves table-valued function references.
   */
@@ -109,6 +108,19 @@ object ResolveTableValuedFunctionsSeq extends Rule[LogicalPlan] {
       }
     ),
 
+    "flagstat" -> Map(
+      /* flagStat(tableName) */
+      tvf("tableName" -> StringType)
+      { case Seq(tableName: Any) =>
+        FlagStatTemplate(tableName.toString, null)
+      },
+      /* flagStat(tableNameOrPath, sampleId) */
+      tvf("tableNameOrPath" -> StringType, "sampleId" -> StringType)
+      { case Seq(tableNameOrPath: Any, sampleId: Any) =>
+        FlagStatTemplate(tableNameOrPath.toString, sampleId.toString)
+      }
+    ),
+
     "coverage" -> Map(
       /* coverage(tableName) */
       tvf("table" -> StringType, "sampleId" -> StringType, "refPath" -> StringType)
@@ -170,6 +182,35 @@ object ResolveTableValuedFunctionsSeq extends Rule[LogicalPlan] {
   }
 }
 
+case class FlagStatTemplate(tableNameOrPath: String, sampleId: String, output: Seq[Attribute])
+  extends LeafNode with MultiInstanceRelation {
+
+  override def newInstance(): FlagStatTemplate = copy(output = output.map(_.newInstance()))
+
+  def toSQL(): String = {
+    s"""
+          SELECT RCount, QCFail, DUPES, MAPPED, UNMAPPED, PiSEQ, Read1, Read2, PPAired, WIaMM, Singletons
+          AS `${output.head.name}`
+          FROM flagStat('$tableNameOrPath')"""
+  }
+
+  override def toString: String = {
+    s"FlagStatFunction ('$tableNameOrPath')"
+  }
+}
+
+object FlagStatTemplate {
+  private def output() = {
+    FlagStat.Schema.toAttributes;
+  }
+
+  def apply(tableNameOrPath: String, sampleId: String) = {
+    new FlagStatTemplate(tableNameOrPath, sampleId, output());
+  }
+}
+
+
+
 
 object PileupTemplate {
 
diff --git a/src/main/scala/org/biodatageeks/sequila/utvf/SequilaSession.scala b/src/main/scala/org/biodatageeks/sequila/utvf/SequilaSession.scala
index 931cb6c7..96e62e00 100644
--- a/src/main/scala/org/biodatageeks/sequila/utvf/SequilaSession.scala
+++ b/src/main/scala/org/biodatageeks/sequila/utvf/SequilaSession.scala
@@ -10,6 +10,7 @@ import org.apache.spark.sql.execution.datasources.SequilaDataSourceStrategy
 import org.apache.spark.sql.functions.{lit, typedLit}
 import org.apache.spark.sql.internal.SessionState
 import org.apache.spark.sql.types.{ArrayType, ByteType, MapType, ShortType}
+import org.biodatageeks.sequila.flagStat.{FlagStatRow, FlagStatStrategy}
 import org.biodatageeks.sequila.pileup.PileupStrategy
 import org.biodatageeks.sequila.rangejoins.IntervalTree.IntervalTreeJoinStrategyOptim
 import org.biodatageeks.sequila.utils.{InternalParams, UDFRegister}
@@ -33,8 +34,8 @@ object SequilaSession {
         new SequilaDataSourceStrategy(spark),
         new IntervalTreeJoinStrategyOptim(spark),
         new PileupStrategy(spark),
+        new FlagStatStrategy(spark),
         new GenomicIntervalStrategy(spark)
-
       )
     /*Set params*/
     spark
@@ -111,6 +112,16 @@ case class SequilaSession(sparkSession: SparkSession) extends SparkSession(spark
       new Dataset(sparkSession, PileupTemplate(path, refPath, true, quals), Encoders.kryo[Row])
   }.as[Pileup]
 
+  /**
+   * Calculate flagStat
+   *
+   * @param tableNameOrPath BAM file path or Table
+   * @param sampleId sample id
+   * @return pileup as Dataset[FlagStatRow]
+   */
+  def flagStat(tableNameOrPath: String, sampleId: String) : Dataset[FlagStatRow] ={
+    new Dataset(sparkSession, FlagStatTemplate(tableNameOrPath, sampleId), Encoders.kryo[Row])
+  }.as[FlagStatRow]
 }
 
 
diff --git a/src/test/scala/org/biodatageeks/sequila/tests/flagStat/FlagStatTestBase.scala b/src/test/scala/org/biodatageeks/sequila/tests/flagStat/FlagStatTestBase.scala
new file mode 100644
index 00000000..df9bcbbd
--- /dev/null
+++ b/src/test/scala/org/biodatageeks/sequila/tests/flagStat/FlagStatTestBase.scala
@@ -0,0 +1,50 @@
+package org.biodatageeks.sequila.tests.flagStat
+import com.holdenkarau.spark.testing.{DataFrameSuiteBase, SharedSparkContext}
+import org.apache.spark.sql.{SequilaSession, SparkSession}
+import org.apache.spark.storage.StorageLevel
+import org.biodatageeks.sequila.utils.InternalParams
+import org.scalatest.{BeforeAndAfter, FunSuite}
+
+import java.io.File
+import scala.reflect.io.Directory
+
+class FlagStatTestBase extends FunSuite
+  with DataFrameSuiteBase
+  with BeforeAndAfter
+  with SharedSparkContext{
+
+  System.setSecurityManager(null)
+
+  val sampleId = "NA12878.multichrom.md"
+  val bamPath: String = getClass.getResource(s"/multichrom/mdbam/${sampleId}.bam").getPath;
+  val tableName = "reads_bam"
+  var ss : SequilaSession = null;
+
+  def cleanup(dir: String) = {
+    val directory = new Directory(new File(dir))
+    directory.deleteRecursively()
+  }
+
+  val flagStatQuery =
+    s"""
+       |SELECT *
+       |FROM  flagstat('$tableName', '${sampleId}')
+    """.stripMargin
+
+  before {
+    spark.sqlContext.setConf(InternalParams.SerializationMode, StorageLevel.DISK_ONLY.toString());
+    spark.conf.set("spark.sql.shuffle.partitions", 1);
+    ss = SequilaSession(spark);
+    ss.sparkContext.setLogLevel("ERROR");
+    ss.sqlContext.setConf(InternalParams.BAMValidationStringency, "SILENT");
+    ss.sqlContext.setConf(InternalParams.UseIntelGKL, "true");
+    ss.sqlContext.setConf(InternalParams.IOReadAlignmentMethod, "hadoopBAM");
+    ss.sql(s"DROP TABLE IF EXISTS $tableName");
+    ss.sql(s"""
+							|CREATE TABLE $tableName
+							|USING org.biodatageeks.sequila.datasources.BAM.BAMDataSource
+							|OPTIONS(path "$bamPath")
+							|
+     	""".stripMargin);
+  }
+}
diff --git a/src/test/scala/org/biodatageeks/sequila/tests/flagStat/FlagStatTestSuite.scala b/src/test/scala/org/biodatageeks/sequila/tests/flagStat/FlagStatTestSuite.scala
new file mode 100644
index 00000000..9d62a1c5
--- /dev/null
+++ b/src/test/scala/org/biodatageeks/sequila/tests/flagStat/FlagStatTestSuite.scala
@@ -0,0 +1,57 @@
+package org.biodatageeks.sequila.tests.flagStat
+
+import org.apache.avro.io.Encoder
+import org.apache.spark.sql.{DataFrame, SequilaSession}
+import org.biodatageeks.sequila.flagStat.{FlagStat, FlagStatRow}
+import org.biodatageeks.sequila.utils.Columns
+import org.biodatageeks.sequila.tests.flagStat.FlagStatTestBase;
+
+class FlagStatTestSuite extends FlagStatTestBase {
+  test("Against a stable implementation (samtools)") {
+    val result = ss.sql(flagStatQuery);
+    performAssertions(result);
+    println("Base Test (against known-working implementation) passed");
+  }
+
+  test("Dataframe API testing") {
+    val testDF = ss.flagStat(tableName, sampleId).toDF();
+    val rdd = ss.sparkContext.parallelize(Expected.toSeq);
+    val exptDF = FlagStat(ss).processDF(rdd);
+    assertDataFrameEquals(exptDF, testDF);
+    println("DF API Test passed");
+  }
+
+  test("SQL DF against API testing") {
+    val result = ss.sql(flagStatQuery);
+    val rdd = ss.sparkContext.parallelize(Expected.toSeq);
+    val exptDF = FlagStat(ss).processDF(rdd);
+    assertDataFrameEquals(exptDF, result);
+    println("SQL DF against API Test passed");
+  }
+
+  val Expected = Map[String, Long](
+    "RCount" -> 22607,
+    "QCFail" -> 0,
+    "DUPES" -> 1532,
+    "MAPPED" -> 22277,
+    "UNMAPPED" -> 330,
+    "PiSEQ" -> 22607,
+    "Read1" -> 11309,
+    "Read2" -> 11298,
+    "PPaired" -> 21647,
+    "WIaMM" -> 21924,
+    "Singletons" -> 353
+  );
+
+  private def performAssertions(df:DataFrame):Unit ={
+    assert(df.count() == 1);
+    val obtained = df.where("RCount > 0");
+    assert(obtained.count(), 1);
+    val results = obtained.first();
+    Expected.foreach(kv => {
+      println(s"Checking: ${kv._1} == ${kv._2}...");
+      val index = results.fieldIndex(kv._1);
+      assert(results.getLong(index), kv._2);
+    })
+  }
+}