The pain relief provided by regular intramuscular diclofenac and on demand intramuscular papaveretum was compared over a 48 h postoperative period in 114 patients undergoing total hip replacement. The study was of a randomised, single-blind, between-group design. Patients were assessed by a surgeon, physiotherapist and nursing staff. Diclofenac was more effective than papaveretum in pain control (P less than 0.001), wound tenderness (P less than 0.01), awareness (P less than 0.001) and mobilisation (P less than 0.01). Wound drainage (P greater than 0.05) and wound oedema (P greater than 0.05) were not significantly different in the two treatments. Gastrointestinal complications were encountered in both groups; two patients on diclofenac had to be withdrawn because of them. The use of diclofenac given as a postoperative analgesic is rewarding, particularly in patients undergoing musculoskeletal procedures. Patients will be more comfortable and will mobilise better during their whole postoperative course.