Five patients, four women and one man, between the ages of 19-38 years developed nonsystemic renal glomerular disease. All presented with proteinuria (two with the nephrotic syndrome) and four had microhematuria. Biopsy revealed mesangial and focal proliferative glomerulonephritis with "full house" immunofluorescence (deposits containing IgG, IgM, IgA, C1q, C4, C3). The deposits were located primarily in the mesangium. After 10-58 months of follow-up, none has demonstrated any evidence of systemic illness. All had persistent proteinuria and two have shown evidence of progression of disease but none was in established renal failure. Because of the "full house" immunofluorescence, this entity resembles mesangial lupus nephritis and may be the nonsystemic counterpart of the latter illness analogous to the proposed relationship of IgA nephropathy to Henoch-Schönlein nephritis.