A child will be evaluated for 3 weeks before he/she is assigned randomly (like tossing a coin) to receive either fluvoxamine or an inactive placebo for 8 weeks. After this double-blind phase (neither the child/parents nor the doctor know which treatment is being given), the child will have the option of continuing treatment during a 4-month open-label extension period (both the child/parents and the doctor know which the child is receiving).