I usually wear a size 9.5 street shoe, but I took the advice of other reviewers and ordered a half size larger. When standing with my weight on my feet, my foot is 10 3/8" long (26.5 cm) and 3 7/8" wide (9.5 cm) at the widest point (across the ball of the foot). These size 10 mediums fit quite snugly about the toes, even with my foot pushed all the way back into the heel. I can feel my toes hitting the end just slightly. I can wear them with nylons, but not with a thin cotton peds or anything thicker. My past experience with Capezios leads me to expect they will stretch a bit, so I am not sending them back. After one evening's dance, I suspect they will be perfect.

The arch support feels a little too far back  (towards the heel) for me. Still, these are very lovely looking shoes, very well balanced and slick as the dickens! I can imagine many happy hours twirling on the dance floor without torquing my knees.

UPDATE: After wearing them to a couple dances, I can report that I probably should get the size 10.5. Toes are just too squashed! Arch support is indeed worthless due to its placement too far back in the shoe. They will make very pretty dress shoes, but for heavy-duty dancing, I'm afraid they're just not going to cut the rug (ha ha).