Try: from itertools import * l = [1,2,3,4,5,6] i = iter(l) for x,y in izip(i,i): print "%d %d" % (x,y) Under CPython you get the expected: 1 2 3 4 5 6 Under IronPython I got: 2 2 4 4 6 6 This is under: IronPython console: IronPython 1.1a1 (1.1) on .NET 2.0.50727.42 Oli