We measured pyrazinamide and rifampicin plasma concentrations in five patients with pulmonary tuberculosis and end stage renal failure treated by haemodialysis or continuous ambulatory peritoneal dialysis. Using conventional daily doses of oral pyrazinamide and rifampicin, we found that the drugs were removed efficiently by both dialysis methods, so that plasma levels were sub-optimal for maximal bactericidal action. These findings suggest that in patients with tuberculosis on maintenance dialysis, treatment should be either with higher doses of these two drugs, or with additional replacement doses given after each dialysis. Further detailed pharmacokinetic studies on larger numbers of patients are indicated.