We report 2 years' experience managing 39 preteen (ages 4-12 years) children with patient-controlled analgesia (PCA) for pain associated with bone marrow transplantation (BMT). We prescribed morphine or hydromorphone PCA (starting bolus 20 micrograms/kg morphine or 2 micrograms/kg hydromorphone) with or without continuous infusion (CI), for a period of 6-74 days. The duration of PCA use (median 19 days) depended upon severity of mucositis or other painful conditions. The peak morphine use was on the 11th day after BMT. We prescribed CI opioids in addition to PCA, either at night or around the clock, in 52% of patients. Ninety-five percent of children successfully mastered PCA to control pain associated with BMT. We observed no instances of drug misuse, parental tampering, accidental overdose, or difficulty weaning from opioids. We conclude that opioid PCA, with or without CI, over several days or weeks is safe and effective for preteen children suffering BMT-related pain.