This study will determine if methylphenidate improves fatigue in men undergoing hormonal therapy for prostate cancer. Fatigue is a common problem experienced by cancer patients. Those patients who are receiving chemotherapy or radiation are especially vulnerable to fatigue, as are men with prostate cancer who are receiving hormonal therapy with an LHRH-agonist (androgen deprivation therapy). Eligible men will be randomized to a daily dose of 10 mg methylphenidate or placebo for a total treatment period of 12 weeks. Subjects will be monitored for changes in fatigue and mood during this period. While the exact cause of fatigue in this setting is unknown, this study will hopefully lead to a better understanding of the process and provide patients with a much-needed remedy for fatigue