diff --git a/src/MultiSet.java b/src/MultiSet.java
new file mode 100644
index 0000000..e79ec63
--- /dev/null
+++ b/src/MultiSet.java
@@ -0,0 +1,15 @@
+abstract class MultiSet {
+
+    /*
+    An abstract class representing the MultiSet ADT, which supports the
+    add, remove, is_empty, count, and contains operations.
+
+    This class itself does not handle how the underlying data is stored.
+     */
+    abstract boolean add(Object item);
+    abstract boolean remove(Object item);
+    abstract boolean contains(Object item);
+    abstract boolean is_empty(Object item);
+    abstract int count(Object item);
+    abstract int size();
+}