The efficacy of epidural hydromorphone alone or in combination with epinephrine for postoperative analgesia was evaluated in 30 healthy women who underwent cesarean delivery with epidural anesthesia. They were assigned randomly to receive either 1.5 mg hydromorphone alone (N = 15) or 1.5 mg hydromorphone with 1/200,000 epinephrine (N = 15). Duration of analgesia (mean +/- SD) was 24.3 +/- 9.4 hours after the epidural injection of hydromorphone plus epinephrine. This was significantly greater (p less than 0.01) than the duration of 18.2 +/- 5.9 hours after the same dose of plain hydromorphone. Analgesia was more rapid in onset and significantly better at the 0.5, 1, 3, and 12 hours postoperatively in the hydromorphone-epinephrine group. Side effects including pruritus (73%), nausea (20%), and vomiting (15%) were of similar frequency with and without epinephrine. Although mean venous PCO2 (PvCO2) levels three and six hours after the hydromorphone-epinephrine dose were elevated significantly over the pre-drug PvCO2 levels, no respiratory depression was detected by an apnea monitor to which all patients were connected. The addition of epinephrine to epidural hydromorphone hastened onset and prolonged the duration of analgesia after cesarean section.