The polyol pathway has long been associated with diabetic retinopathy. Glucose is converted to sorbitol with the aid of the enzyme aldose reductase. Aldose reductase inhibitors can prevent changes induced by diabetes. A total of 30 patients with minimal background retinopathy were randomly divided into a ponalrestat-taking group and a placebo-taking group. All were followed for 6 months and twenty-three were followed for 12 months. The baseline microaneurysm count was 2.6 +/- 1.9 (mean +/- SD) for the ponalrestat group and 3.5 +/- 2.9 for the placebo group. At 6 months the counts were 3.1 +/- 3.5 and 2.9 +/- 3.6 and after 12 months 3.0 +/- 4.1 and 2.9 +/- 3.4. There is no statistically significant difference between the groups at 0, 6 or 12 months of study. The change in retinopathy severity level did not significantly differ between the two groups at either 6 or 12 months. Ponalrestat administration at a dosage of 600 mg daily for 12 months has no significant effect on the course of minimal retinopathy in diabetic patients.