After reading these reviews, I was able to narrow my size options down to Tall XS or Tall S (I'm 140lbs, 5'10" with an average size rear, and am typically a M in leggings or 6 in pants). I ordered both sizes and honestly spent too long in front of the mirror trying to figure out which worked better..., b/c THEY BOTH FIT, lol. In spite of the style being considered a bit oversized, neither option I tried was loose around the rear. In fact, both fit my rear the same (not snug, but certainly not baggy), and the only detectible difference I could see was that the legs and waistband were a touch looser in the S vs the XS -- though the silhouette was similar for both. I thought about keeping the XS and returning the S in case the material relaxed while wearing as some joggers can do, but opted to risk sticking with the S in case they shrink a bit after washing. But in reality, these are basic sweatpants, even if they are Athleta (and believe me, I am brand loyal to Athleta!). I'm all for paying extra for sweatpants that are cozier, fit better and have the extra details to make them look nicer, but these are *very* similar in look/feel to another brand I have from a certain big box retailer at a fraction of the price. In the end, I'm keeping these b/c I LOVE the red color, but at this price point, the value is hard to defend given how fiddly the sizing is and the uncertainty of how they'll wear over time. If you're dying to try these then by all means, go for it! But if you're on the fence, maybe hang on and wait for a sale. Inflation has been real, y'all. :)