Pharmacokinetics of lithium were studied in 4 females acutely intoxicated with lithium with maximal plasma concentrations of 8.7, 4.0, 3.4 and 1.3 mmol/l. Mean plasma dialysance values were 103, 105, 102 and 89 ml/min compared to mean renal clearance values of 13, 16, 20 and 30 ml/min, respectively. A rebound effect in plasma concentration suggested that the sum of the dialysance and renal clearance overestimated the total body clearance of lithium during hemodialysis. During hemodialysis the measured half-lives of the plasma lithium levels in three cases were 4.8, 3.4 and 2.3 hours compared to the corrected values of 12.0, 7.3 and 6.2 hours respectively, when this rebound effect was taken into consideration. These corrected half-lives were 30-66% of the control half-lives recorded later when each patient served as her own control, thus illustrating the effectiveness of hemodialysis in removing lithium. Forced diuresis with sodium chloride did not significantly increase renal lithium elimination.