diff --git a/toolz/itertoolz.py b/toolz/itertoolz.py
index 354ecf25..1e0c81ac 100644
--- a/toolz/itertoolz.py
+++ b/toolz/itertoolz.py
@@ -332,6 +332,11 @@ def tail(n, seq):
         drop
         take
     """
+    if n <= 0:
+        try:
+            return seq[0:0]
+        except (TypeError, KeyError):
+            return tuple()
     try:
         return seq[-n:]
     except (TypeError, KeyError):
diff --git a/toolz/tests/test_itertoolz.py b/toolz/tests/test_itertoolz.py
index c8640917..3b486865 100644
--- a/toolz/tests/test_itertoolz.py
+++ b/toolz/tests/test_itertoolz.py
@@ -189,6 +189,13 @@ def test_tail():
     assert list(tail(3, 'ABCDE')) == list('CDE')
     assert list(tail(3, iter('ABCDE'))) == list('CDE')
     assert list(tail(2, (3, 2, 1))) == list((2, 1))
+    # tail(0) used to return the whole sequence because -0 == 0
+    # slices from the start; see issue #626
+    assert tail(0, 'ABCDE') == ''
+    assert tail(0, (3, 2, 1)) == ()
+    assert tail(0, [1, 2, 3]) == []
+    assert tail(0, iter('ABCDE')) == ()
+    assert tail(-2, [1, 2, 3]) == []
 
 
 def test_drop():