I agree w/ Susan! I wear a Sidi road shoe size 39 *regular width and I have a narrow foot, thats how narrow they run* and in street shoes I normally buy a 7N. I also have a pair of Pearl Izumi tri shoes in a 37.5. That just shows you how small the Sidi shoes run. You might try experimenting with a slightly thicker than normal cycling sock as well. I wear a running sock instead and it works like a charm.