I have a now 5 year old autistic son who my husband and I have been trying to potty train for several years now to no avail...until recently.  He was great going to the potty on his own if he was naked or just had pants or shorts on but no diaper, but as soon as we put underwear on him he would pee.  We tried regular underwear, boxer briefs, even the pullups that have the "cool" feeling - nothing.  He just didn't care or didn't notice the need to go to the bathroom.  Then a friend of my mother's said she had a similar problem with her little boy and started putting him in boxers and they did the trick.  Boxers allowed that "free" feeling that gave our son the ability to feel the sensation that he had to use the restroom as opposed to the restricted feeling that the regular underwear did (he confused the tight feeling as the same as wearing a diaper).  We aren't fully potty trained yet, but we are so much closer than we were before.  Now our son runs to the bathroom on his own or tells us he has to go instead of just peeing in his pants.  I only wish that I could find these in the store instead of having to buy online.