The steady state disposition of chloroquine and its major metabolites, monodesethyl and bidesethyl chloroquine, were determined in 6 patients on long-term treatment for rheumatic disease with 99-155 mg base/day. The total body clearance of chloroquine was 0.35 l/kg/h and that of its metabolites was much higher. The renal clearance was the same for all compounds measured, approximately equal to 0.1 l/kg/h. Currently recommended dosage schedules appear to be too high in certain cases.