The authors studied 10 patients with non-insulin-dependent diabetes mellitus and 5 controls matched for age, sex, blood lipids, and smoking habit. The two groups were also comparable for hemorheologic characteristics as evaluated by viscosimetry on whole blood, plasma and serum, erythrocyte filtration and aggregation. The microcirculation was studied in the subjects of both groups by microalbuminuria determination, retinal fluorangiography, and capillaroscopic examination of the bulbar conjunctive and nail folds. None of the patients presented microalbuminuria values higher than the upper limit of normal (20mg/24h). Fluoroangiographic alterations were observed in 4 patients, and all 10 presented capillaroscopic alterations at the bulbar conjunctiva (microaneurysms, erythrocyte aggregates) and nail folds (more frequently of the fingers than toes). Similar alterations were detected in controls. Thus these abnormalities seem independent of hemorheologic values.