I am a 36C and ordered this in a M.  It fits well and is really comfortable.  The only issue I have with this bra is that getting it on is pretty tough.  It twists in the back and getting it over my chest is a little difficult.  Getting it off requires some work too.  Aside from that, once it's on I have no problems with it.  If I had to order another one it would probably be in a L.