Summary Initial S35 tissue levels were higher in jaundiced than in control rats following S35-prochlorperazine administration. However, 8 hours later tissue levels were lower in jaundiced rats. After this time tissue levels decreased very slowly in jaundiced rats and at 48 hours were considerably higher than in control animals. A major portion of the dose administered to jaundiced rats was excreted in the urine, while fecal excretion is the predominant route in control rats. In view of findings by other investigators it is likely that the altered drug disposition observed in jaundiced rats is the cause of the delayed death phenomenon observed in these animals.