IgA lambda multiple myeloma was diagnosed in a 58-year-old white woman after the onset of nephrotic syndrome. Serial renal histology demonstrated progressive mesangial proliferative glomerulonephritis. Electron microscopy revealed subepithelial electron dense deposits. Immunofluorescence microscopy demonstrated granular staining of peripheral capillary loops with IgG and C3. No IgA was present. No evidence of deposition of the myeloma protein in the glomeruli was found. The temporal relationship of occurrence of the two diseases and the progression of glomerular disease suggest that multiple myeloma be added to the list of malignancies causing immune complex glomerulone-phritis.