Metabolic fate of carpipramine in rats and rabbits was examined by chemical assay, and the effect of this drug on serotonin levels in rat brain was also investigated. When a small dose was given orally, its absorption from the gastrointestinal tract was rapid but its absorption rate decreased when a relatively large dose was given orally in rats. The concentration of this drug in plasma and other tissues of rabbits was usually higher than that in rats. Carpipramine was concentrated in the lung, liver, and spleen, but only a small amount of the drug was found in the brain in both animal species. The half-life of this drug in plasma was 0.9 hr for rats and 2.3 hr for rabbits. Its excretion in urine was about 2% of the administered dose and about 13% in the feces within 2 days after oral administration to rats. When carpipramine was administered intraperitoneally, serotonin levels increased and reserpine-induced release of serotonin was inhibited in rat brain.