We describe a 35-year-old woman who had nodular glomerulosclerosis associated with deposition of fragmented gamma (gamma 1)-heavy chains. She presented with edema of lower legs, mild proteinuria, and hematuria. Laboratory examination revealed hypocomplementemia, and a small amount of monoclonal IgG-lambda (lambda) in the blood. Renal biopsy disclosed prominent nodular expansion of the mesangium. Ultrastructurally, the nodules were composed of electron dense deposits and fibrillar structures. An immunofluorescent study showed depositions of gamma-heavy chains and C3 in the central portion of nodules and capillary walls, whereas kappa (kappa)-, lambda-light chains, and Fab fragments of the heavy chain were negative. The accumulation of collagen I, IV, V, and VI was demonstrated in the mesangium. Western blot analysis of serum protein disclosed fragmented gamma-heavy chains that did not combine with light chains. Glomerular nodular lesions, thus, can occur in heavy chain deposition disease, as in light chain deposition disease. Fragmented gamma-heavy chains may also induce hypocomplementemia by the activation of the complement pathway.