One hundred adolescents undergoing posterior spinal fusion for scoliosis were reviewed to assess the adequacy of postoperative patient-controlled analgesia. There were 94 females and 6 males. The mean settings for morphine dosage were a loading dose of 114.5 micrograms.kg-1, a bolus dose of 24.8 micrograms.kg-1, and a lockout interval of 9.9 minutes. This was used for an average of 75.8 h, with a 52.2% success rate. Adolescents using patient-controlled analgesia showed a great variability in morphine requirements with greater use as they became older. The requirement was not significantly different on the 1st, 2nd and 3rd postoperative days and the total consumption was 52.2 micrograms.kg-1.h-1. Nausea and vomiting occurred in 45% and pruritus in 15%. There were 7 cases of respiratory depression who all recovered promptly and completely. This method is associated with high morphine requirements in adolescents, but can be used safely.