We compared patient-controlled analgesia (PCA) and continuous infusion (CI) morphine delivery in a randomized controlled trial in adolescents during oropharyngeal mucositis pain after bone marrow transplantation. Results from 20 patients who completed 7 or more days on study (10 PCA, 10 CI) were evaluated. The group means for age, weight and height were comparable. Daily measures were morphine intake, self-report of pain intensity and side effect scores. Over 10 study days, the mean cumulative morphine dose to subjects in each group was 4.94 mg/kg (PCA) vs. 12.17 mg/kg (CI); the difference is significant (P less than 0.01). No significant differences were found between the groups for patient ratings of pain intensity or side effect scores despite the large difference in mean morphine intake, but the PCA group tended to report less intense sedation and less difficulty concentrating. Adolescents can use PCA effectively and safely for 1-3 weeks. Morphine intake of adolescent patients using PCA morphine intake is significantly lower than that of similar patients receiving staff-controlled CI.