Tramadol is a centrally acting analgesic agent that is increasingly being used to treat pain in cats, though limited data are available on analgesic efficacy. Six healthy adult cats were used in this study to determine the thermal antinociceptive effect of the oral administration of tramadol at doses between 0.5 and 4 mg/kg in cats. An antinociceptive effect refers to reduction of sensitivity to painful stimuli. Results showed that doses of 2 mg/kg and higher were necessary to yield a significant and sustained effect. All six cats exhibited mydriasis (dilated pupils) after administration of 3 and 4 mg/kg. Three of the six cats appeared to have a facial itch at different doses of 2, 3, and 4 mg/kg, respectively. No clinically important adverse effect was observed in the cats though this study was not designed to assess the safety of tramadol in cats. This study suggests that a dose of 4 mg/kg given every 6 hours will maintain analgesia close to the maximum effect of tramadol. [VT]