We hypothesized that combined femoral-sciatic nerve block (FSNB) offers better analgesia with fewer side effects than intraarticular infiltration (IA) in children undergoing anterior cruciate ligament (ACL) reconstruction. Thirty-six children undergoing ACL reconstruction were randomized to FSNB or IA. FSNB patients had FSNB with bupivacaine (0.125%)-clonidine (2 microg/kg), whereas IA patients received bupivacaine (0.25%)-clonidine (1 microg/kg)-morphine (5 mg). Postoperatively, analgesia was provided with patient-controlled analgesia and rescue morphine. Patient demographics were similar. FSNB patients required less intraoperative fentanyl (50 +/- 40 microg versus 80 +/- 50 microg; P = 0.04). Visual analog scale score for FSNB was smaller than IA in the recovery room (1.8 +/- 3 versus 5.4 +/- 3; P = 0.0002) and during the first 24 h (1.6 +/- 1 versus 2.9 +/- 2; P = 0.01)). FSNB morphine use in the first 18 h was less (7 +/- 13 mg versus 21 +/- 21 mg; P = 0.03). Fewer FSNB patients vomited (11% versus 50%; P = 0.03). IA patients required morphine patient-controlled analgesia sooner. After ACL reconstruction in children, FSNB with bupivacaine-clonidine provides better analgesia with fewer side effects than IA with bupivacaine-clonidine-morphine.