OUTLINE: This is a randomized, double-blind, placebo-controlled, two arm study. Patients are stratified according to initial fatigue level (high vs moderate), and treatment with tumor vaccine (yes vs no). Patients are randomized to one of two treatment arms. Arm I: Patients receive oral methylphenidate twice daily. Arm II: Patients receive oral placebo twice daily. Treatment is continued for 21 consecutive days with dose escalations as tolerated and as needed by patient judgement, followed by an additional week to evaluate the effect of drug withdrawal. Patients are contacted by telephone at least twice weekly during the 21 day treatment and 7 day washout phase to assess adverse or rebound effects. Before the study begins and at weekly clinic visits for the 4 week study period, patients complete a series of questionnaires to measure mood, levels of fatigue and lethargy, and sense of well being. Patients also keep a short daily diary of study medication doses and degree of tiredness. Patients are followed every 3 months for 2 years, then every 6 months for the next 3 years, and then annually thereafter.