The elimination half-time and renal clearance of lithium was measured in 12 schizophrenic patients. Minimum plasma lithium concentrations during alternate dosage intervals in 5 patients increased rapidly during the first 2 to 3 days of treatment and reached a steady state level after 5 to 6 days. After the establishment of the remaining 7 patients on lithium the decline in plasma lithium concentration when treatment was stopped was monoexponential. Elimination half-times ranged from 19.3 to 41.3 hours (mean +/- SD = 28.9 +/- 7.9h) and were significantly correlated with renal creatinine clearance (p less than 0.01). Renal lithium clearances ranged from 13.5 to 36.8 ml/min (mean +/- SD = 24.4 +/- 8.0 ml/min) and the apparent volumes of distribution ranged from 0.39 to 1.39 L/kg (mean +/- SD = 0.79 +/- 0.34 L/kg). There was no evidence that the elimination parameters of lithium in schizophrenic patients were significantly different from those in healthy individuals or manic-depressive patients.