True to size, but it fits tight.  Perfect for me.  I use it for Brazilian Jiu Jitsu.  I also plan on using it for whitewater rafting and scuba diving - either under a wetsuit or by itself.  Bonus! its got UV protection.  That makes it smell a little weird, but its not bad. I haven''t actually used it yet, only tried it on.

I work as a lifeguard at a Summer camp and wanted to stay protected from the sun. I am a thin-average size 4-6 but ordered the XL for comfort and it was still skin tight.

Great quality!!! So much better than whatever I had last year which completely came apart (not the same product or color). But obviously beware of the farmer's/everything else but your stomach, chest, and back tan. Otherwise perfect, form-fitting, sucks in my jiggle, and keeps me kinda warmer in the mornings.