The aim of this prospective, randomized, double-blind study was to compare the effects of adding either preservative-free morphine, 0.2 mg (n = 20), epinephrine, 0.2 mg (n = 21), or a combination of both (n = 29) to hyperbaric bupivacaine in parturients having elective cesarean sections during spinal anesthesia. Ten additional patients receiving spinal bupivacaine alone were studied as the Control Group. High-pressure liquid chromatography with a sensitivity of 20 micrograms/mL was used to measure serum bupivacaine in all subjects. The results showed that the spread and regression of the sensory and motor blocks were similar among the study groups. However, the intraoperative analgesia was superior in patients receiving bupivacaine combined with morphine and epinephrine, whereas there was no difference between those given an addition of either morphine or epinephrine. Postoperative analgesia was the shortest and opioid requirement in the first 24 h the most with epinephrine alone. No respiratory depression occurred. The neonatal condition was excellent in all groups. Serum concentrations of bupivacaine at 10 min, at delivery (25 +/- 1.4 min), and at 60 min after the intrathecal injection were similar among the groups including the Control Group. The concentrations of bupivacaine in umbilical arterial and venous sera were less than the sensitivity level of the analytical method. We conclude that the addition of 0.2 mg of morphine plus 0.2 mg of epinephrine to hyperbaric bupivacaine improves the intra- and postoperative analgesia without an added risk. This improvement is not due to vasoconstriction and a reduction in the absorption of bupivacaine from the subarachnoid space.