During the first phase of the study which is of 8-days duration subjects will receive placebo on some days and methylphenidate on others. During this phase of the study the effects of the medication on children's performance on a computerized test of attention will be assessed. Individuals who do not have significant methylphenidate side effects during the first phase of the study will then participate in the second phase of the study. During the second phase subjects will receive either methylphenidate or placebo for 8 weeks. Neuropsychological measures of attention, memory, behavioral inhibition, cognitive flexibility, and motor performance will be obtained at baseline and after the 8 week medication trial in order to assess methylphenidate effects on the rate of recovery. Recovery will also be assessed using an interview measure of adaptive behavior and cognitive functioning. A stimulant medication side effect rating scale will be used to monitor for common methylphenidate adverse effects throughout both phases of the study