I started putting our 2 year 4 month old son in these 5 days ago to start the potty training process.  Our son is about 36" tall and 26 pounds--I bought the 2T and they were a wee bit big on him, but they shrank to fit after washing.  There is just enough extra padding in the crotch that if he starts to go and then stops to get to the potty his pants aren't wet.

I highly recommend these over pullups--you might be doing a few more loads of laundry, but I find the potty training results far quicker and consistent in the "big boy" undies.

My only complaint is these are $5 overpriced here--I got them for $7.99 at the bullseye store after I had already ordered here.