We retrospectively studied 101 children with Tourette's syndrome to characterize the early course of illness and associated behavioral disturbances of attention deficit hyperactivity disorder (ADHD), obsessive-compulsive disorder (OCD), disruptive behavior (DB), and school problems (SP). For patients without ADHD (45%), OCD (50%), DB (67%), or SP (52%) at the time of initial evaluation, 13% developed ADHD, 8% OCD, 28% DB, and 25% SP during the observation period of 1.6 +/- 1.3 years (range, 0.5 to 7 years). For patients with behavioral disturbances initially, the problems were controlled or resolved for many over time and with therapy: ADHD, 46%; OCD, 47%; DB, 50%; and SP, 67%. Medication changes, assessed after a drug adjustment period between the initial and first follow-up visits (6 +/- 6 months), showed that drug dosages remained largely unchanged and few patients required the addition of new drugs: tic suppressants, 10%; anti-obsessional agents, 5%; and stimulants, 12%. Tic suppressants were withdrawn from 12%.