OBJECTIVES: I. Determine whether methylphenidate decreases fatigue and lethargy in cancer patients receiving interferon alfa. II. Determine whether the use of methylphenidate in this patient population decreases the number of dose reductions of interferon alfa due to toxicities other than myelosuppression or elevated liver function tests. III. Assess whether efficacy or toxicity of methylphenidate in this patient population is concentration dependent. IV. Compare the fatigue subscale and the proposed Brief Fatigue Inventory.