I do underwear but they have to have a leakproof plastic pant over the top that the child can pull up and down themselves.... Kids know that pull-ups are just diapers and that they can pee in them and so they do ..... I have never actually had a kid use the pull-up like underwear and not pee in them ski think they are a waste of time. I currently have one training and he comes in a diaper and I immediately bring him to the potty and I take off his diaper and pants and put thick underwear on him and then about every 20 mins I say " remember xxxxx you are wearing big boy underwear and you cannot pee in them " if after one hour he has not independently used the potty I say "ok xxxx it's time to use the potty " I've been doing this for two weeks now and not had an accident.... I put him back in his diaper when we go outside and to go home.