There are very few data on the molecular biology of hepatitis C virus (HCV) infection in dialysis patients. 101 patients undergoing dialysis treatment in 4 units in the Lombardy, northern Italy, were analyzed by RT-PCR for HCV viremia, by line probe assay technology for HCV genotyping and by a serological analysis for detecting type-specific antibodies. 61 of 101 (60%) patients showed detectable HCV RNA in serum; HCV genotype 2a was dominant (30/ 53 = 57%), followed by HCV genotype lb (20/53 = 37%). There was no relationship between HCV genotyping and the clinical or demographic features of the patients. The antibody response toward the c33-c, cl00-3, and 5-1-1 antigens was more frequent in HCV genotype lb compared with genotype 2a (p = 0.046, p = 0.001 and p = 0.0001, respectively). The antibody levels to NS-3 and NS-4 HCV proteins were significantly higher in patients with HCV genotype lb in comparison with HCV 2a-infected individuals (p = 0.0001). There was a high level (82%) of agreement between HCV genotyping by RT-PCR and the assessment of type-specific antibodies by serological analysis; further, it was possible to detect type-specific antibodies in 6 of 22 (27%) patients in whom PCR amplification was unsuccessful. In conclusion, HCV subtype 2a was dominant in our population of HCV-infected dialysis patients, dialysis patients infected by different genotypes showed similar demographic and clinical characteristics, the antibody response toward the NS-3- and NS-4-related antigen of HCV was genotype dependent. There was a high level of agreement between HCV genotyping by RT-PCR and the detection of type-specific antibodies by serological analysis. As significant biological differences may exist among HCV strains, the assessment of HCV types may be very useful in the routine clinical activity of nephrologists in dialysis units.