Six domestic shorthair cats, aged three to four years and weighing 5·1 to 7·4 kg, were used to assess the thermal antinociceptive effect of a transdermal buprenorphine patch, designed to supply 35 μg buprenorphine/hour, which was applied to the shaved thorax. The cats' thermal thresholds were tested before the patch was applied and two, four, six, eight, 10, 12, 14 and 16 hours after it had been applied, and then every six hours until it was removed after 72 hours, and for a further 24 hours afterwards. Blood was collected at each time to measure the plasma concentration of buprenorphine. The patches did not produce a significant change in the thermal thresholds of the cats throughout the testing period. The mean (sd) peak plasma buprenorphine concentration was 10 (0·81) ng/ml.