PATIENT CHARACTERISTICS: Age: 18 and over Performance status: Not specified Life expectancy: More than 4 weeks Hematopoietic: Hematocrit at least 30% Hepatic: Not specified Renal: Creatinine no greater than 2.0 mg/dL Other: No history of any of the following: Chronic use of anticonvulsants Seizure disorder Motor tics Glaucoma Family history or diagnosis of Tourette's disorder No allergic reaction or hypersensitivity to methylphenidate Cognitively able to participate Not incarcerated Not pregnant or nursing Fertile patients must use effective contraception