BACKGROUND The authors studied the addition of bupivacaine and epinephrine, separately and together, to epidural fentanyl to determine whether this improved postcesarean analgesia and reduced the incidence of side effects. METHODS After elective cesarean section, 100 parturient patients who received fentanyl (3 microg/ml) epidurally for 48 h were allocated randomly in a double-blinded manner to four groups to receive, in addition to the study solution, 0.01% bupivacaine, 0.5 microg/ml epinephrine, both, or neither. A neurologic assessment of breast-fed neonates was made at 2 and 48 h of life. Plasma fentanyl concentrations were determined in a subset of patients at intervals after treatment. RESULTS Patients receiving fentanyl alone made more attempts at patient-controlled analgesia (P < 0.01), required a greater total dose of fentanyl (P < 0.01), reported more pain (P < 0.003) and less satisfaction (P < 0.003), and had more nausea and urinary retention (P < 0.05) than all other groups. Patients who received bupivacaine with or without epinephrine had better overall satisfaction scores than those who did not receive bupivacaine (P < 0.001), and they required less fentanyl (P < 0.02) than patients who received fentanyl with only epinephrine. Motor blockade or orthostatic hypotension did not develop in any patient, and all patients could ambulate without difficulty. Neurobehavioral scores, which were similar among all neonates, were within the normal range. Plasma concentrations of fentanyl increased after epinephrine-containing solutions were discontinued. CONCLUSIONS During the conditions of this study, the addition of epinephrine and bupivacaine to a 3-microg/ml epidural fentanyl solution for postcesarean section pain relief provided superior analgesia compared with fentanyl alone or fentanyl with epinephrine. Whether increasing the concentration of fentanyl alone might improve the efficacy of fentanyl remains unclear.