I usually wear a 42. My size tends toward narrow - Italian shoes in regular width fit great and Nine West swim on me. Since these don't have a back I buy a 1/2 size down. I got 10 reg and they were too wide. They also worn down in the heel in a really strange place - to the side forcing my foot almost out of the show. I decided to try again with the narrow. They fit great and are wearing more in the center of the heel but still fit strange. The shoe feels like it wants to force my heel to the side. I probably would not buy these again but they look really nice and I wear the current pair often. The first pair only lasted one month so the narrow works much better.