The pharmacokinetics of detomidine, a novel analgesic sedative, was studied in the major target species after high (80 μg/kg) i.v. and i.m. doses. In addition, drug residues in some organs were determined. Concentrations were measured using a sensitive, detomidine‐specific radio‐immunoassay method. Rapid absorption following i.m. dosing occurred. Absorption half‐lives were 0.15 h (horse) and 0.08 h (cattle). The mean peak concentration in the horse (51.3 ng/ml) was achieved in 0.5 h and in the cow (65.8 ng/ml) in 0.26 h. The areas under the concentration curve after i.m. dosing were 66% (horse) and 85% (cow) of the corresponding i.v. values. Distribution was rapid with half‐lives of 0.15 h (horse, i.v.) and 0.24 h (cow, i.v.). The apparent volume of distribution was higher after the i.m. dosing (horse 1.56 Vkg, cow 1.89 l/kg) than after i.v. dosing (horse 0.74 l/kg, cow 0.73 Vkg). Elimination half‐lives were 1.19 h (horse) and 1.32 h (cow) for the i.v. dose and 1.78 h (horse) and 2.56 h (cow) for the i.m. dose. Total clearances ranged from 6.7 (horse, i.v.) to 12.3 (cow, im.) ml/min/kg. Renal clearances were less than 1 % of the total clearances showing negligible excretion of the drug in urine and suggesting elimination by metabolism. A cross‐reacting metabolite in urine corresponded to less than 1.5% of the detomidine dose's immunoreactivity. High‐dose detomidine increased urine flow significantly. Excretion of detomidine in milk in cattle was extremely low. No detectable amounts were present 23 h after dosing. Jktomidine did not accumulate in tissues. All tissue concentrations measured 48 h after dosing were less than 3% of the original dose per weight unit. Both magnitude and duration of the drug's action closely paralleled its serum pharmacokinetics. In this respect no difference between equine and bovine specie