diff --git a/src/yaku.erl b/src/yaku.erl
index 724ff78..e650d10 100644
--- a/src/yaku.erl
+++ b/src/yaku.erl
@@ -13,6 +13,7 @@
          pinfu/2,
          iipeikou/2,
          chanta/2,
+         itsuu/2,
          chiitoitsu/2,
          kokushi_musou/2,
          ryuu_iisou/2,
@@ -100,6 +101,18 @@ chanta(#game{}, #player{hand=#hand{tiles=[], melds=Melds}}) ->
               end,
               Sets).
 
+%% @doc Returns true for an Itsuu hand
+%%      Hand must contain a 1-9 run in one suit
+-spec itsuu(game(), player()) -> boolean().
+itsuu(#game{}, #player{hand=#hand{tiles=[], melds=Melds}}) ->
+    Tiles = lists:flatten([TS || #meld{type=chii, tiles=TS} <- Melds]),
+    Runs = [lists:filter(fun(#tile{suit=S, value=V}) -> S =:= Suit end, Tiles)
+            || Suit <- [man,sou,pin]],
+    lists:any(fun(TS) ->
+                      sets:from_list([V || #tile{value=V} <- TS]) =:= sets:from_list(lists:seq(1,9))
+              end,
+              Runs).
+    
 %% @doc Returns true for a 7-pair hand.
 -spec chiitoitsu(game(), player()) -> boolean().
 chiitoitsu(#game{}, #player{hand=#hand{tiles=[], melds=Melds}})
diff --git a/test/riichi_yaku_tests.erl b/test/riichi_yaku_tests.erl
index c57dec8..aff85c1 100644
--- a/test/riichi_yaku_tests.erl
+++ b/test/riichi_yaku_tests.erl
@@ -52,6 +52,14 @@ chanta_test() ->
                         #meld{type=chii, tiles=[#tile{suit=man, value=V} || V <- [7,8,9]]}]},
     ?assertEqual(true, yaku:chanta(#game{}, #player{hand=Hand, drawn={tsumo, #tile{suit=dragon, value=red}}})).
 
+itsuu_test() ->
+    Hand = #hand{melds=[#meld{type=pair, tiles=lists:duplicate(2, #tile{suit=sou, value=8})},
+                        #meld{type=chii, tiles=[#tile{suit=sou, value=V} || V <- [1,2,3]]},
+                        #meld{type=chii, tiles=[#tile{suit=sou, value=V} || V <- [4,5,6]]},
+                        #meld{type=chii, tiles=[#tile{suit=sou, value=V} || V <- [7,8,9]]},
+                        #meld{type=chii, tiles=[#tile{suit=man, value=V} || V <- [6,7,8]]}]},
+    ?assertEqual(true, yaku:itsuu(#game{}, #player{hand=Hand, drawn={tsumo, #tile{suit=dragon, value=red}}})).
+
 chiitoitsu_test() ->
     Hand = #hand{melds=[#meld{type=pair, tiles=lists:duplicate(2, #tile{suit=pin, value=V})} || V <- lists:seq(1,7)]},
     ?assertEqual(true, yaku:chiitoitsu(#game{}, #player{hand=Hand})).