Chronic hepatitis C virus (HCV) infection is associated with several extrahepatic syndromes. The principal types of renal disorders associated with chronic HCV infection are cryoglobulinemia or noncryoglobulinemic membranoproliferative glomerulonephritis (MPGN). Interferon-α (IFN-α) may precipitate or exacerbate the occurrence of MPGN. Our patient was a 32-year-old man who tested positive for HCV in July 1997. The patient was treated with IFN-α in another medical center for 6 months because his liver biopsy showed chronic active hepatitis. In December 1998, he applied to our clinic for a follow-up examination. The level of aspartate aminotransferase (AST) was 44 U/L, and that of alanine aminotransferase (ALT) was 69 U/L. HCV RNA was positive in serum, and chronic HCV infection was detected by liver biopsy. IFN-α therapy (5 million U/day) was administered for 6 months longer. In May 1999, the patient came to our polyclinic with edema of the feet and legs. We detected proteinuria, serum cholesterol of 269 mg/dl, AST of 50 U/L, ALT of 41 U/L, serum total protein of 3.4 g/dl, serum albumin of 1.2 g/dl, positive cryoglobulin, and urine protein of 9.84 g/day. Cryoglobulinemic MPGN was suspected and kidney biopsy was performed, resulting in a diagnosis of minimal change disease (MCD).