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Dr. U. Gladziwa, Department of Internal Medicine II, Technical University of Aachen, Pauwelsstrasse 30, D-52057 Aachen (Germany) Dear Sir, With great interest we read the short communication by Caramelo et al. [1], who found hepatitis C virus (HCV) antibodies in 12 hemodialysis and 5 continuous ambulatory peritoneal dialysis patients. All sera of the studied patients were positive for HCV RNA, whereas polymerase chain reaction (PCR) performed on samples of hemodialysis ultrafiltrate or peritoneal effluent were always negative for HCV RNA. We would like to draw your attention to a multicenter clinical study where we investigated the prevalence of anti-HCV in patients on peritoneal dialysis [2]. The reactive sera were confirmed by RIBA, and viremia was determined by PCR. The total prevalence of anti-HCV among the patients studied was 18 out of 333 (5.4%). The prevalence of anti-HCV among the centers ranged from 0 to 30%. Fifteen out of 18 sera reactive by ELISA were positive when tested by RIBA resulting in a prevalence of 4.5%. These sera were considered as truly positive and tested by PCR for viremia. Eleven of the 15 seropositive patients showed HCV RNA in serum when tested by nested PCR, indicating viremia in most of the antibody-positive patients. From the 11 patients whose sera were positive for HCV RNA, 9 dialysates were tested. Seven of 4 showed antibodies by ELISA or HCV RNA, respectively, also in the peritoneal dialysate. There is no doubt that blood transfusion is a source of HCV infection. However, in our study the total duration of dialysis (peritoneal and hemodialysis duration) was found to be a significant risk factor. This correlation implies nosocomial modes of HCV infection. Caramelo et al. [1] could show that a significant group of patients remained HCV antibody negative, although they shared the same dialysis machine with positive patients. However, whether the sharing of hemodialysis machines contributes to HCV transmission remains moreover to be elucidated. For the first time, we detected the presence of antibodies against various structural and nonstructural antigens (C22, C33c, C100) and HCV RNA in the peritoneal dialysate of seropositive peritoneal dialysis patients. Krautzig et al. [3] found in 4 of 5 HCV-RNApositive patients the peritoneal dialysate also positive, at least on 1 of 3 occasions. The HCV RNA was only in 1 case 3 times positive. It is interesting that HCV RNA was detected in serum and dialysate of our studied patients in 73.3 and 44.4%, respectively. This observation