Sorbitol concentration has been measured in retina, optic, and sural nerve of normal, diabetic, and aldose reductase inhibitor-treated diabetic rats. The sural nerve displayed significantly higher sorbitol content than the retina and the optic nerve both in control animals and in diabetic animals. In the sural nerve the response to treatment with an aldose reductase inhibitor was more marked than in the two other tissues. The activities of aldose reductase and sorbitol dehydrogenase were not influenced by diabetes. It is suggested that aldose reductase inhibition may be of greater use for alleviating peripheral nervous system accumulation of sorbitol than for hindering CNS accumulation of the polyol.