This study compared the quality of analgesia and incidence of adverse effects with two doses of intrathecal morphine in patients undergoing elective Caesarean section. Fifty patients were randomly allocated to receive either morphine 0.1 mg or 0.2 mg in addition to a standard intrathecal dose of 2.5 ml bupivacaine 0.5% in 8% dextrose. The quality of analgesia was assessed using visual analogue scores and the incidence of nausea, vomiting and itching were recorded during the first 24 h postoperatively. There was no statistically significant difference in the quality of analgesia nor in the incidence and severity of itching between the two groups. Fewer patients in the 0.1 mg morphine group experienced postoperative nausea and vomiting (7 versus 14, p < 0.05). We conclude that the use of 0.1 mg morphine intrathecally produces comparable analgesia to 0.2 mg after Caesarean section with significantly less nausea and vomiting.