diff --git a/eth2/utils/ssz/src/impl_tree_hash.rs b/eth2/utils/ssz/src/impl_tree_hash.rs
index 9463283cb..7249b7f73 100644
--- a/eth2/utils/ssz/src/impl_tree_hash.rs
+++ b/eth2/utils/ssz/src/impl_tree_hash.rs
@@ -1,5 +1,6 @@
 use super::ethereum_types::{Address, H256};
 use super::{hash, merkle_hash, ssz_encode, TreeHash};
+use std::collections::HashMap;
 
 impl TreeHash for u8 {
     fn hash_tree_root(&self) -> Vec<u8> {
@@ -66,13 +67,57 @@ where
     }
 }
 
+impl<K, V> TreeHash for HashMap<K, V>
+where
+    K: Eq,
+    K: Hash,
+    K: Ord,
+    V: TreeHash,
+{
+    /// Appends the tree_hash for each value of 'self, sorted by key,
+    /// into a byte array and returns the hash of said byte array
+    fn tree_hash(&self) -> Vec<u8> {
+        let mut items: Vec<_> = self.iter().collect();
+        items.sort_by(|a, b| a.0.cmp(b.0));
+        let mut result = Vec::new();
+        for item in items {
+            result.append(&mut item.1.tree_hash());
+        }
+
+        hash(&result)
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
 
     #[test]
     fn test_impl_tree_hash_vec() {
-        let result = vec![1u32, 2, 3, 4, 5, 6, 7].hash_tree_root();
+        let result = vec![1u32, 2, 3, 4, 5, 6, 7].tree_hash();
         assert_eq!(result.len(), 32);
     }
+
+    #[test]
+    fn test_impl_tree_hash_hashmap() {
+        let mut map = HashMap::new();
+        map.insert("c", 3);
+        map.insert("b", 2);
+        map.insert("g", 7);
+        map.insert("d", 6);
+        map.insert("e", 4);
+        map.insert("a", 1u32);
+        map.insert("f", 5);
+        let result = map.tree_hash();
+
+        // TODO: create tests that tie-out to an offical result
+        assert_eq!(
+            result,
+            [
+                130, 215, 165, 255, 224, 6, 144, 225, 14, 139, 67, 238, 205, 240, 20, 173, 53, 0,
+                105, 62, 49, 174, 244, 160, 114, 92, 232, 11, 102, 200, 112, 24
+            ]
+        );
+    }
+
 }
diff --git a/eth2/utils/ssz/src/tree_hash.rs b/eth2/utils/ssz/src/tree_hash.rs
index 913b961ab..6efe41a40 100644
--- a/eth2/utils/ssz/src/tree_hash.rs
+++ b/eth2/utils/ssz/src/tree_hash.rs
@@ -90,6 +90,5 @@ mod tests {
 
         //note: should test againt a known test hash value
         assert_eq!(HASHSIZE, result.len());
-        println!("merkle_hash: {:?}", result);
     }
 }