Single oral and intramuscular doses of 14C-sultopride to rat, rabbit and dog and single oral doses of sultopride to human volunteers were well absorbed. Mean blood levels of total 14C peaked at 0.4-1.1 h and declined with half-lives of 2, 1.5 and 3 h in rat, rabbit and dog, respectively. In man mean serum levels of unchanged drug attained a peak at 1.5 h and were eliminated with a half-life of 3.6 h. Highest concn. of radioactivity were found in rat liver, kidney, hypophysis, submaxillary gland and gastrointestinal tract. The concn. in the cerebrum and cerebellum were low. 14C-Sultopride passed through the placental barrier. 14C-Sultopride was poorly bound to plasma proteins (less than 25% bound) in all species. Repeated doses of the drug slightly increased the blood and tissue levels of 14C in the rat. Most of the dose was eliminated via the kidneys in all species. Male rats excreted larger amounts of 14C into bile and faeces. A high ratio of A.U.C. (milk)/(blood) (c. 3.5) was found in the lactating rat.