Fifty-seven women received extradural morphine 3 mg, buprenorphine 0.18 mg or buprenorphine 0.09 mg after elective Caesarean section carried out under extradural bupivacaine. Supplementary sublingual buprenorphine was available on demand. Ten-centimetre visual analogue pain scores were completed regularly; emesis, pruritus and urinary retention were recorded for 24 h. Patients who received buprenorphine 0.09 mg had more pain, and required more supplementary analgesia, than those who received morphine 3 mg. Pain scores and analgesic requirements after buprenorphine 0.18 mg were not significantly different from either of the other two groups. Emesis was not significantly different in the three groups. More itching occurred after morphine 3 mg and buprenorphine 0.18 mg than after buprenorphine 0.09 mg; pruritus of the face, legs and perineum was more common after morphine than buprenorphine. Twenty-eight percent of patients without a urinary catheter developed retention of urine. Seventy-five to 84% of patients were satisfied with analgesia during the first day after operation. Analgesia and adverse effects were similar when morphine 3 mg or buprenorphine 0.18 mg was given extradurally after Caesarean section.