I followed the advice here and ordered up.  Normally I'm between an 8 and an 8.5, and the 9 fits great--I could even fit a thicker pair of socks in there if I needed to.  They are a little snug getting on and I expect it might be a little difficult to get off without a mess.  It would have been nice if there was one of those little ledges on the back of the heel to make hands-off removal a little easier.  These are super cute in the strawberry pattern.  There's just something nice about cheerful rain gear!  I expect them to come in handy for puddles this fall and winter.  While they aren't tall enough for really deep situations, they should be perfect for commuting.  As always, I tested the waterproof claim by standing in a few inches of bathtub water for about 10 minutes, and they performed well.