Six healthy volunteers participated in a single-dose study of pharmacokinetics and metabolism of oral administration of [3H]-pipethiaden (1 mg). Plasma levels of total radioactivity, urinary excretion and metabolism were analyzed by liquid scintillation counting and radio-TLC. The mean peak plasma concentration of radioactive metabolites was 4.9 ng eq/ml, and the mean elimination half life was 11.5 h. 34% of radioactivity was recovered in 4 days in urine, with only 0.4% present as unchanged drug. Pipethiaden was extensively metabolized by S-oxidation, N-demethylation, and N-oxidation.