Renal biopsy specimens from four adult patients with the Schönlein-Henoch syndrome and complicating renal disease were examined by light and electron microscopy. By light microscopy three patients showed diffuse hypercellularity of intercapillary cells and hyper-plasia of intercapillary cell matrix in almost all glomeruli. From twenty to fifty-five per cent of all corpuscles from these patients had epithelial crescents in Bowman's capsule. In one patient with focal and segmental proliferative changes, but without crescents, focal and segmental thrombosis and necrosis were found. Three patients had moderate to severe glomerular infiltration with Polymorphonuclear leucocytes. Electron microscopy confirmed the proliferation of intercapillary cells and hyperplasia of intercapillary cell matrix. Hypercellularity of visceral epithelial cells and endothelial cells were not found. In the epithelial crescents of Bowman's capsule two cell types could be recognized: dark cells and light cells. In between these cells basement membrane-like material was demonstrated. Electron dense deposits were seen in the subendothelial space of the basement membrane, and in the cytoplasm of endothelial cells. To a lesser degree, similar deposits were found in the intercapillary region, in the subepithelial space, and in visceral epithelial cells. No “humps” were observed.