Twenty-five type I diabetics (9 men, 16 women) with a mean disease duration of 19.9 years and 25 sex- and age-matched healthy control subjects were studied. Digital capillary blood flow measurements in combination with a local cooling test were assessed by nailfold videocapillaroscopy using the technique of flying spot and compared with nailfold capillary microscopy in four subgroups divided according to (A) disease duration, (B) retinopathy, (C) fasting blood glucose level, and (D) HbA1c values. Differences in morphologic capillary diameters and capillary density were found between the diabetics and the healthy control subjects. These were attributable to the patients with retinopathy. The hemodynamic findings at rest and after local cooling were unable to differentiate either between type I diabetics and healthy controls or within the different subgroups.