Hepatitis C is both a cause and a complication of chronic renal disease. Chronic infection with hepatitis C virus (HCV) can lead to the immune complex syndromes of cryoglobulinemia and membranoproliferative glomerulonephritis (MPGN). The pathogenetic mechanisms for these conditions have not been defined, although they are clearly caused by the chronic viral infection. Management of HCV-related cryoglobulinemia and MPGN is difficult; antiviral therapy is effective in clearing HCV infection in a proportion of patients, but these conditions can be severe and resistant to antiviral therapy. Hepatitis C also is a complicating factor among patients with end-stage renal disease and renal transplants. The source of HCV infection in these patients can be nosocomial. Screening and careful attention to infection control precautions are mandatory for dialysis units to prevent the spread of hepatitis C. Prevention of spread is particularly important in these patients because HCV infection is associated with significant worsening of survival on dialysis therapy, as well as after kidney transplantation. Furthermore, therapy for hepatitis C is problematic, only partially effective, and associated with significant side effects in this population. There are significant needs in both basic and clinical research in the pathogenesis, natural history, prevention, and therapy for hepatitis C in patients with renal disease.