In a two-year study of 36 diabetic patients with retinopathy, proliferative in 18, first six months (period A) were spent in baseline. The patients then received calcium dobesylate, 250 mg three times a day (period B) and were then entered into the double blind part of the study, receiving either dobesylate for six months followed by placebo for a further six month period, or the reverse, according to a randomised code (period C and D). Cutaneous capillary resistance (CCR) which was abnormal in 26 patients at the beginning of the study had returned toward normal in 11 patients by the end of period B. However, this beneficial effect was not confirmed in the double blind part of the study. Punctate red spots (microaneurysms and microhemorrhages) were counted at the end of each period. No statistically significant differences were noted at any period studied. Retinal angiographic studies also failed to demonstrate any beneficial effect of the drug.