An 18-year-old-woman, with dermatitis herpetiformis, acute glomerulonephritis, malabsorption and villous atrophy due to massive infiltration of IgA producing plasma cells was studied. By light microscopy, her renal biopsy specimen showed heavy immunofluorescence for IgA, a mixed proliferative and membranous lesion with occasional crescents and focal sclerosis. Electron microscopic examination revealed three main lesions: (1) swelling and bleb formation in endothelial cells, (2) extensive fusion of foot processes of podocytes, and (3) a dense quasi-linear, continuous deposition of immune complexes, encompassing several loops; they were characteristically located within the basement membrane at the boundary between the lamina densa and the lamina rara interna. At occasional points where the immune complexes had reached the outer aspects of the basement membrane, there was damage to the podocyte cytoplasm. This electron microscopic aspect supports the interpretation that these immune complexes, although non-complement fixing, exhibit a high damaging potential, leading to relentless disease progression.