Sedation may be a dose-limiting side-effect of opioid therapy in some cancer patients. This study was designed to evaluate further the use of the psychostimulant, methylphenidate, an agent that has been reported to counter-act opioid-induced sedation, in patients with cancer-related pain. Patients receiving a stable dose of an opioid for cancer-related pain were recruited for this randomized, double-blind, crossover clinical trial. In addition to their regular dose of narcotics, they received 5 days of methylphenidate followed by 5 days of placebo, or vice versa. Our data did not definitively demonstrate any statistically significant benefit for methylphenidate, but did suggest that this drug could mildly decrease narcotic-induced drowsiness and could increase night-time sleep. These data, in conjunction with other published data, suggest that methylphenidate can counteract narcotic-induced daytime sedation to a limited degree.