A group of 7 chronically ill, male, schizophrenic patients living on the same ward over a period of at least a year were studied. Spectrophotometric measurements of approximately 3,600 urine specimens were performed in order to determine the excretion pattern of free chlorpromazine and the 3 chlorpromazine sulfoxides which were identified on paper chromatograms.The average excretion of free chlorpromazine and its sulfoxides combined during the period of continuous medication with chlorpromazine at dosage of 100 mg. to 400 mg. t.i.d. ranged from 1.31 to 20.54% of the administered dose. Of this, free chlorpromazine was usually found to be less than 1%, while the sulfoxides ranged from 1 to 18% of the administered dose. The average ratio of free chlorpromazine to its sulfoxides was found to be approximately 1 to 16. After the medication was stopped, free chlorpromazine and its sulfoxides disappeared from the urine within 5 days.