Diabetes mellitus is often complicated by nephropathy with progression to renal failure. Various forms of glomerulonephritis have been associated with diabetes, sometimes resulting in more rapid deterioration in renal function and occasionally dictating alternative management of these patients in attempts to reverse or contain nephrosis or renal failure. We report the occurrence of Type I membranoproliferative glomerulonephritis (MPGN) with hepatitis C virus (HCV) infection in two patients, in association with diabetic nephropathy. One patient had cryoglobulinemia and cryoglobulin deposits in the kidney. A brief review of the literature on glomerulonephritides occurring in patients with diabetes mellitus is also presented. Clinicians should be aware of the possible occurrence of Type I MPGN and cryoglobulinemia in patients with diabetes mellitus and HCV infection with the appropriate history and physical findings. The therapeutic approach to managing patients with two distinct concurrent lesions remains unresolved.