This study evaluates morphologically the sural nerves of two patients with acute and another pair with chronic uremia, both of whom had neither clinical nor electrophysiologic evidence of neuropathy. Morphometric changes indicative of myelin repair were noted in the chronic uremic case who had a shorter duration of renal failure but required dialysis. Also, changes suggestive of axonal degeneration were found in the case who had chronic uremia of long duration. Both cases of acute uremia did not reveal significant abnormalities. Structural changes in the sural nerves may precede clinical and nerve conduction derangements in uremia, specifically in chronic cases.