Thirty healthy male dogs were randomly assigned to receive carprofen (4 mg/kg intravenously), ketoprofen (2 mg/kg intravenously) or saline (0.2 ml/kg intravenously) at induction of anaesthesia for castration surgery. A routine castration was undertaken and a buccal mucosal bleeding time was assessed at the completion of surgery. Twenty-four hours after surgery a 24–hour endogenous creatinine clearance study was undertaken. Buccal mucosal bleeding time was not significantly different between the three groups. Creatinine clearance was significantly lower (P ≤ 0.01) in the two groups of dogs that received a non-steroidal anti-inflammatory drug compared with that in the dogs that received sterile saline. There was no significant difference between the carprofen and ketoprofen groups with respect to creatinine clearance.