A randomized, prospective trial of patient-controlled analgesia (PCA), that is, a method of analgesia administration involving a computer-driven pump activated by patients to receive small doses within defined limits was performed in 82 children and adolescents after major orthopedic surgery to compare (1) intramuscularly administered morphine, (2) PCA morphine and (3) PCA morphine with a low-dose continuous morphine infusion (PCA-plus). Patients receiving PCA and PCA-plus had lower pain scores and greater satisfaction than patients receiving intramuscularly administered morphine. The three groups used equal amounts of morphine and most measures of recovery were identical in the groups. In particular, PCA and PCA-plus did not increase the incidence of opioid-related complications, and patients receiving PCA-plus were less sedated than patients receiving intramuscular therapy. We conclude that PCA and PCA-plus are safe and effective methods of pain relief in children and adolescents after orthopedic surgery, are better accepted than intramuscular injections, and do not increase perioperative morbidity.