diff --git a/larray/src/main/scala/xerial/larray/LArray.scala b/larray/src/main/scala/xerial/larray/LArray.scala
index bc4d1e7..affd1dc 100644
--- a/larray/src/main/scala/xerial/larray/LArray.scala
+++ b/larray/src/main/scala/xerial/larray/LArray.scala
@@ -274,6 +274,9 @@ trait LArray[A] extends LSeq[A] with WritableByteChannel {
   @inline def putLong(offset: Long, v: Long) = { unsafe.putLong(address + offset, v); v}
   @inline def putDouble(offset: Long, v: Double) = { unsafe.putDouble(address + offset, v); v }
 
+  @inline def casInt(offset: Long, exp: Int, v: Int) = { unsafe.compareAndSwapInt(null, address + offset, exp, v) }
+  @inline def casLong(offset: Long, exp: Long, v: Long) = { unsafe.compareAndSwapLong(null, address + offset, exp, v)}
+
 }
 
 
@@ -813,6 +816,10 @@ class LIntArray(val size: Long, private[larray] val m: Memory)(implicit val allo
     v
   }
 
+  def cas(i: Long, exp: Int, v: Int) = {
+    unsafe.compareAndSwapInt(null, m.address + (i << 2), exp, v)
+  }
+
   /**
    * Byte size of an element. For example, if A is Int, its elementByteSize is 4
    */
@@ -849,6 +856,10 @@ class LLongArray(val size: Long, private[larray] val m: Memory)(implicit val all
     v
   }
 
+  def cas(i: Long, exp: Long, v: Long) = {
+    unsafe.compareAndSwapLong(null, m.address + (i << 2), exp, v)
+  }
+
   def view(from: Long, to: Long) = new LArrayView.LLongArrayView(this, from, to - from)
 
 }
diff --git a/larray/src/test/scala/xerial/larray/LArrayTest.scala b/larray/src/test/scala/xerial/larray/LArrayTest.scala
index 87e3806..401925b 100644
--- a/larray/src/test/scala/xerial/larray/LArrayTest.scala
+++ b/larray/src/test/scala/xerial/larray/LArrayTest.scala
@@ -98,6 +98,58 @@ class LArrayTest extends LArraySpec {
       }
     }
 
+    "implement cas correctly" in {
+      info("cas test")
+
+      val l = new LIntArray(3)
+      try {
+        l(0) = 1
+        l(1) = 2
+        l(2) = 3
+        l(0) should be (1)
+        l(1) should be (2)
+        l(2) should be (3)
+
+        l.cas(0, 1, 2) should be (true)
+        l(0) should be (2)
+
+        l.casInt(0, 2, 3) should be (true)
+        l(0) should be (3)
+
+        l.cas(0, 1, 1) should be (false)
+        l(0) should be (3)
+      }
+      finally {
+        l.free
+      }
+    }
+
+    "implement cas correctly for LLongArray" in {
+      info("cas test")
+
+      val l = new LLongArray(3)
+      try {
+        l(0) = 1
+        l(1) = 2
+        l(2) = 3
+        l(0) should be (1L)
+        l(1) should be (2L)
+        l(2) should be (3L)
+
+        l.cas(0, 1L, 2L) should be (true)
+        l(0) should be (2L)
+
+        l.casLong(0, 2, 3) should be (true)
+        l(0) should be (3L)
+
+        l.cas(0, 1L, 1L) should be (false)
+        l(0) should be (3L)
+      }
+      finally {
+        l.free
+      }
+    }
+
     "read/write data to Array[Byte]" taggedAs ("rw") in {
       val l = LArray(1, 3)
       val b = new Array[Byte](l.byteLength.toInt)