The effects and pharmacokinetics of thiopental were studied in eight patients undergoing renal transplantation. The results were compared with findings in a group of patients with normal renal function. No differences were observed in induction doses or between arterial or venous sleep concentrations. The average V3 in the renal failure group was 1441 or 2.5 times the value of the control group (P less than 0.01). The apparent differences indicating longer elimination half-lives and higher serum clearances in the renal patients were not significant. The average binding of thiopental to serum protein shortly after the induction was 83.9% (78.2-88.1) in the renal patients and 89.0% (85.2-91.6) in the control patients (P less than 0.05). The difference in V3 could be explained by the differences in protein binding and when the serum clearance was calculated by using the unbound fraction, this "intrinsic clearance" was significantly lower in the renal failure group (P less than 0.05). Haemodynamic parameters were determined during the initial 5 min. No significant difference was observed between the thiopental-induced changes in stroke volume. Cardiac output was unchanged in both patient groups.