diff --git a/README.md b/README.md
index c5237a8..8c4d307 100644
--- a/README.md
+++ b/README.md
@@ -112,7 +112,7 @@
   * SELECT index ✓
   * SETBIT key offset value
   * SETEX key seconds value ✓
-  * SETNX key value
+  * SETNX key value ✓
   * SETRANGE key offset value
   * SHUTDOWN
   * SINTER key [key ...]
diff --git a/index.html b/index.html
index e10bda7..1e9b053 100644
--- a/index.html
+++ b/index.html
@@ -464,6 +464,13 @@ <h3>Scenarios</h3>
         assert_equal(l.get("foo"), "Hello")
       },
 
+      "SETNX should set a key only if the key does not exists": function(){
+        l.setnx("foo", "Hello");
+        l.setnx("foo", "World");
+
+        assert_equal(l.get("foo"), "Hello");
+      },
+
     });
 
   </script>
diff --git a/lodis.coffee b/lodis.coffee
index 5be0da9..3c98ef7 100644
--- a/lodis.coffee
+++ b/lodis.coffee
@@ -343,3 +343,5 @@ class @Lodis
     this.set(key, value)
     this.expire(key, expire)
 
+  setnx: (key, value) -> this.set(key, value) if !this.exists(key)
+
diff --git a/lodis.js b/lodis.js
index 9a6511b..59d2100 100644
--- a/lodis.js
+++ b/lodis.js
@@ -536,6 +536,11 @@
       this.set(key, value);
       return this.expire(key, expire);
     };
+    Lodis.prototype.setnx = function(key, value) {
+      if (!this.exists(key)) {
+        return this.set(key, value);
+      }
+    };
     return Lodis;
   })();
 }).call(this);