['Despite the potential importance of endoneurial microvessel abnormalities in diabetic neuropathy, the pathogenesis of these abnormalities is incompletely understood. We wished to evaluate the effect of experimental diabetes on endoneurial microvessels and determine if an aldose reductase inhibitor alters any of the changes induced by diabetes.', 'We compared streptozocin diabetic rats with and without aldose reductase inhibitor treatment to non-diabetic rats after 10 months of diabetes. Transverse microvessels from the mid-sciatic level were studied by electron microscopic morphometric evaluation.', 'Microvessel endothelial, pericyte, basement membrane and total mural area were greater in untreated diabetic animals than non-diabetic animals. Aldose reductase inhibitor treated diabetic animals had greater endothelial area and possibly pericyte area but not basement membrane or total mural area.'] Are nerve microvessel changes in diabetes prevented by aldose reductase inhibition?