Aspirin dosages calculated from published pharmacokinetic data were tested in 3 male and 3 female Basset Hounds. Emesis occurred frequently after dosing at the rate of 50 mg/kg of body weight, a dosage that would be required for a convenient 12-hour dosing interval. A dosage of 25 mg/kg every 12 hours avoided emesis but did not maintain serum salicylate concentrations within the desired range of 10 to 30 mg/100 ml. A dosage of 25 mg/kg every 8 hours resulted in serum salicylate concentrations varying from 12.5 to 17.8 mg/100 ml. It was concluded that a maintenance dosage of 25 to 35 mg/kg every 8 hours in optimal for the dog, based on extrapolation of data obtained in man.