Forty dogs undergoing a variety of orthopaedic surgical procedures were randomly assigned to one of two analgesic protocols, receiving either pethidine at 2 mg/kg pre-operatively and 3 mg/kg postoperatively, or carprofen, a new non-steroidal anti-inflammatory drug at 4 mg/kg pre-operatively. Analgesia and sedation were assessed after the operations under double blind conditions using a discontinuous scoring system and a visual analogue scale. There was good agreement between the two scoring systems, and a statistical analysis of the visual analogue scores showed that carprofen provided slightly better pain relief than pethidine and produced less sedation. Carprofen provided good analgesia during the 18 hours the dogs were in hospital and no adverse side effects were observed.