In this prospective randomised study, pruritus and pain were evaluated in patients undergoing abdominal surgery in which intrathecal morphine was administered. Each patient received intrathecal morphine 0.3 mg prior to induction, followed by a standard anaesthetic. The patients were randomly allocated to one of two groups. One group received 100 mg of rectal diclofenac immediately post-induction. Patients receiving diclofenac had significantly lower pruritus scores at 30 min (p = 0.0076), 2, 4, 8 and 24 h postoperatively, as well as significantly reduced pain scores at each time point (p < 0.0001 at each study interval). Morphine consumption in the first 24 h was also significantly lower in this group. In conclusion, rectal administration of diclofenac significantly reduces the incidence and severity of postoperative pruritus. It also significantly reduces pain and further analgesic requirements postoperatively.