The prevalence of antibodies to the hepatitis C virus (HCV) was determined in 333 peritoneal dialysis (PD) patients from 10 German dialysis units, using an enzyme-linked immunosorbent assay of the second generation (ELISA 2nd gen) which detects antibodies to a structural (C22) and to non-structural (C33c, C100, 5-1-1) recombinant antigens of HCV Sera from 18/333 (5.4%) patients were anti-HCV positive versus 11/295 (3.7%) when the sera were tested by an ELISA of the first generation (ELISA 1st gen) containing only a non-structural antigen (C100). In the 18 sera positive by ELISA 2nd gen, antibodies against at least one viral protein were found by recombinant immunoblot assay (RIBA) in 15/333 (4.5%) patients. In the sera of 11/15 (73.3%) patients HCV RNA was detected by nested PCR. Epidemiological evaluation of the patients revealed that the prevalence of anti-HCV was correlated to the female sex (p = 0.005), presence of anti-HBc (p = 0.006), duration of total dialysis (hemodialysis HD and PD) (p = 0.012), duration of HD alone (p = 0.025) and previous renal transplantation (p < 0.001). Only a weak correlation was found to blood transfusions (p = 0.041) and elevation of serum ALT concentration (p = 0.055). But no correlation was found to diagnoses of renal failure (p = 0.129), duration of PD (p = 0.963) and past surgical procedures (p = 1.0). Four of nine peritoneal dialysates of anti-HCV positive patients were found positive for HCV RNA. In conclusion: 1. The prevalence of anti-HCV is lower in patients on PD than in those on HD. 2. There is a high rate of viremic patients. 3. The peritoneal dialysate is infectious and represents a risk for the transmission of HCV.