I chose to purchase these sandals on Amazon for the free returns, and I am glad I did.  I was unsure what size to get since this was my first purchase of Birkenstocks, and the first pair I ordered (37) seemed a bit too large.  When my heel was all the way back in the heel cup (as it is supposed to be, according to the fitting instructions on a few websites I read), there was about 1/2 inch left at the top of my big toe.  I also had to tighten the straps to the tighest setting.  I returned the pair for a size 36, and these seem to fit much better, and give more support.  I almost always wear size 7, but occasionally 6.5 in some brands (maybe 1 out of every 5 pairs of shoes I purchase).  So these definitely run big.  I haven't broken them in yet, and I can tell that it may take some time, but I will do it gradually like you are supposed to.  Overall, I'm excited to wear them this summer, and happy for the price I got them at.  I originally got the black, but got the golden brown when I got the smaller size.  I didn't particually like the black birko-flor strap as much.