I had both of my autistic sons 100% trained by age 3 1/2. If your son is showing signs he's ready, then I highly recommend using a kitchen timer, and training him on the toilet with a potty seat (like Baby Bjorn) from the beginning--instead of using a separate potty chair--otherwise you may find transitioning to the toilet like starting over!
Have them only wear a long shirt--no pull ups or underwear. Set timer for 20 minute intervals...bell rings, accompany him to the potty. Keep him there for at least 15-20 minutes (talk about being a big boy, sing songs, read potty books, sit near him to keep him company). Offer lots of juice/water! If unsuccessful, let him up, set the timer for about 10-15 minutes and go again! If he's "overdue" keep the breaks short, to avoid an accident, and to hopefully get him to go in the potty! Have him wear just a long shirt--no underwear/pull ups--it'll make him more "body conscious."
at 10:58 AM on Mar. 8, 2009