I bought a size up from what I was, per everyones recommendation, and they were still too small.  They grabbed at my junk, then chafed the inside of my legs to practically bleeding.  I tried wearing these on 3 separate occasions; once on a hike, once on a day on Baltimore where I walked in 90 degree weather for 10 hours, and once walking through New Orleans in July for the evening.  Every time they chafed me to a point of I wanted to just take them off and free ball it.  I have been wearing cheap joe boxer 'boxer briefs' for years and wanted something better.  You would think with the reputation of under armour and the high price I would get a steller product, well in my case you would be wrong.  Perhaps I just have oddly shaped twig and giggle berries, I dunno, but these things were just the worst boxer briefs I have ever worn.  The only 100% effective boxer briefs that I have are the Exoffico type.  I tried one out a couple of times, worked fantastic, bought another also works fantastic.  Ive worn them both about 10 times each and have never ever had a problem.  Oh, and their sizes are actually correct vs the oddly sized underarmour AND are about 30% cheaper.

Maybe I need a size smaller or a size larger, I don't know.  But for the price of these things I guess I will never find out.