Glomerular ultrastructure was studied in 12 long-term insulin dependent diabetic patients with fairly advanced nephropathy. This article discusses the observation of capillary profiles in the glomerular tuft of a deviating ultrastructure: the basement membrane (BM) is focally extremely thin and in between it presents a very loose fluffy texture, resembling the BM in immature glomeruli. Such thin-walled capillaries (TWC) constituted 1 to 5% of total capillary length and surface. The second observation reported here is the presence of vessels within the BM of Bowman's capsule. These capillaries were lined with fenestrated endothelium, and the capsular epithelium sometimes presented foot process formation. It is suggested that both types of capillaries represent new vessel formation in the renal corpuscle in these cases of advanced diabetic glomerulopathy.