The administration of epidural opioids, though effective for producing analgesia, has severe side effects in most patients. It is unknown whether clonidine can effectively replace opioids and cause fewer side effects. We compared, in this randomized trial, the incidence of vomiting and pruritus as well as the analgesic profile of three different combinations of bupivacaine, fentanyl, and clonidine administered epidurally in patients undergoing the Nuss procedure: bupivacaine + fentanyl, bupivacaine + clonidine, bupivacaine + fentanyl + clonidine. The incidence of side effects was significantly less in the bupivacaine + clonidine group (33%) compared with the bupivacaine + fentanyl (92%) and bupivacaine + fentanyl + clonidine (73%) groups (P = 0.004). Quality of postoperative analgesia was similar in the three groups. No significant complications were observed. In conclusion, clonidine is an effective and safe alternative to epidural opioids.