Hepatitis C virus (HCV) infection has been associated with several renal pathologies, including membranoproliferative and membranous glomerulonephritis. Although the presence of HCV proteins has been reported, there are no data concerning detection of the viral RNA in renal cells from HCV-infected patients with kidney disease. In this report we analysed, by in situ hybridization, the presence of HCV RNA in renal biopsies from 10 patients who were positive for antibodies to HCV (anti-HCV) and serum HCV RNA positive, and from four patients without HCV infection, with different renal disease. HCV RNA was detected in the renal biopsies from all of the 10 HCV-infected patients. Hybridization signals were detected in the tubular and capillary endothelial cells. No hybridization signals were found in the renal biopsies of the four anti-HCV-negative patients. In conclusion, our results demonstrate that HCV RNA is common in kidney cells of patients with renal diseases who are infected with HCV. The presence of HCV RNA is not necessarily associated with a pathogenetic consequence.