A novel renal complication was reported in a patient with angiofollicular lymph node hyperplasia (Castleman's Disease), who developed acute renal failure due to membranoproliferative glomerulonephritis. Renal biopsy showed marked mesangial hyperplasia, basement membrane thickening with subendothelial electron-dense deposits, interstitial plasma cell infiltration, and glomerular deposition of IgM and complement components. A resolution of systemic manifestations and an improvement in renal function followed prednisolone and azathioprine therapy. Disease relapse, with increasing proteinuria and the development of factor 8 inhibitor, occurred 3 months later. Sustained remission was achieved with prednisolone and cyclophosphamide therapy, which were given for 42 and 12 months, respectively. Renal biopsy during remission showed significant resolution of the mesangial hyperplasia and disappearance of interstitial plasmacytic infiltration as well as subendothelial electron-dense deposits.