The authors evaluated the efficacy and incidence of side effects from blockade of the femoral nerve with 0.5% bupivacaine in 14 children with fracture of the middle third of the femoral shaft. In nine of these children, a pharmacokinetic analysis was also performed. The onset of analgesia occurred in 8.0 +/- 3.5 minutes after blockade of the femoral nerve. One block failed, resulting in iv narcotics being administered to alleviate the pain. In the remaining 13 children, pain decreased to nonexistent in 11 of the children and only mild pain with movement in the remaining two children. The level of analgesia did not change when the children underwent radiographic examination (60 +/- 18 min after the femoral nerve block) and application of traction (124 +/- 19 min after femoral nerve block). The maximum bupivacaine plasma concentration was 0.89 +/- 0.37 microgram/ml, obtained 24.4 +/- 12.6 min after the end of the injection. The femoral nerve blockade with bupivacaine provides prompt, effective, and prolonged analgesia in children suffering from fractures of the femoral shaft, allowing transport, radiographic examination, and application of traction in optimal conditions. Although the sample size was small, the side effects appeared to be rare.