Hepatitis C virus (HCV) infection may be associated with extrahepatic illness including renal disease. We investigated the clinical and virological characteristics of three patients who developed a mesangial proliferative and sclerosing glomerulopathy alone or in association with membranoproliferative glomerulonephritis after liver transplantation for end-stage liver disease secondary to HCV infection. Using polymerase chain reaction technology and the IgM RlBA assay, viral load, genotype and IgM antibody response to HCV in the setting of glomerulonephritis was evaluated. Within 1 year of transplantation, the patients showed decreased renal function, proteinuria and recurrent hepatitis C liver disease. Likewise, HCV viral load increased following transplantation, whereas the viral genotypes remained unchanged. Although the first patient presented with classic type II cryoglobulinemia in association with glomerulonephritis, the second patient developed an epatitis C virus (HCV) infection is a major H cause of chronic hepatitis and cirrhosis.Chronic HCV infection also is associated with at least two types of glomerular injury; membranoproliferative glomerulonephritis (MPGN)5-7 and membranous glomerulonephritis.8 Additionally MPGN seen in the setting of HCV is often accompanied by variable degrees of mesangial proliferation and s c l e r~s i s .~.~*~ HCV-related MPGN is frequently seen in conjunction with a positive rheumatoid factor, hypocomplementemia, circulating immune complexes (as detected by the Clq binding assay) and cryogl~bulinemia.~~~J~ Viral RNA, anti-HCV immunoglobulin (Ig)G and rheumatoid factorlike IgM activity have been charac-