The purpose of this study was to examine the effect of pretransplant interferon administration on the occurrence of post-transplant de novo glomerulonephritis in hepatitis C virus (HCV)-positive renal allografts. From December 1992 to December 2000, 78 HCV-positive patients received a renal allograft in our unit. Fifteen out of 78 received pretransplant interferon for 1 year. Hepatitis C virus was investigated by serology and qualitative polymerase chain reaction (PCR). Hepatitis C virus-related de novo glomerulonephritis (membranoproliferative or membranous) was suggested by proteinuria (>1.5 g/24 h) and/or microhematuria and always diagnosed by renal biopsy. Of 15 HCV-positive recipients who received pretransplant interferon, 10 (67%) became HCV-RNA negative at the time of transplantation and only one out of the 15 (6.7%) developed de novo glomerulonephritis (this patient was HCV-RNA positive at transplantation). Among non-interferon-treated allograft recipients, 28.7% had negative HCV-RNA and 12 out of 63 (19%) developed de novo glomerulonephritis (9, membranoproliferative; 3 membranous), all 12 having positive HCV-RNA at transplantation (p < 0.0001). In conclusion, pretransplant interferon may reduce the occurrence of post-transplant HCV-related de novo glomerulonephritis. Our results suggest that the indication for pretransplant interferon should be extended to treat all HCV-RNA positive candidates for renal transplantation.