Lithium kinetics were studied in 14 patients with lithium poisoning. Three patients were treated by hemodialysis. Serum lithium peak concentrations ranged between 1.4 and 9.6 mmol/L. The apparent mean serum half-life was 23.16 +/- 9 h, the mean total clearance was 26.5 +/- 13.3 mL/min and the mean renal clearance was 17.2 +/- 5.4 mL/min. The kinetic parameters were dependent on the duration of the study and on the type of the poisoning: acute, acute upon chronic or chronic. During the first 12 h after admission ten patients were in a distribution phase, three were in an elimination phase and one was in an absorption phase. The serum half-life during hemodialysis ranged from 3.6 to 5.7 h and hemodialysis clearance was 63.2 to 114.4 mL/min. The mean volume of distribution calculated in six cases was 0.63 +/- 0.09 L/kg. The evolution of the lithium pools showed a different kinetic pattern between the extra- and the intracellular pool which decreased more slowly. During hemodialysis the decrease of the extracellular pool was about twice that of the cellular pool. Among the factors which may modify lithium toxicity and kinetics, are the type of the poisoning, the presence of an underlying disease and renal impairment. No general and rigid indication for hemodialysis can be set, but the need for hemodialysis should be based on clinical and kinetic data determined during the 12 h following admission.