Arteriolar vasomotion, the cyclic contraction/dilation of terminal arterioles, is disordered in diabetes. The aim of the present study was to characterize the impairment of cutaneous vasomotion in type 1 and type 2 diabetes, especially with regard to the influence of metabolic control and to the response to shear stress. Twenty type 1 and 23 type 2 diabetic patients were investigated. Vasomotion waves were recorded in single capillaries at the dorsal middle phalangeal area of the left ring finger during rest, after warming the skin temperature to 33 degrees C, and after 3-min arterial occlusion by means of laser Doppler anemometry. Suprasystolic occlusion caused an increase in amplitudes of vasomotion only in type 1 diabetic patients (0.12 +/- 0.04 mm/s vs. 0.36 +/- 0.06 mm/s, p = 0.001). In type 1 but not in type 2 diabetic patients, both systolic and diastolic blood pressure correlated positively with amplitudes of resting vasomotion (r = 0.62, p = 0.002 and r = 0.65, p = 0.001, respectively). Amplitudes of vasomotion after warming up at frequencies of 5 - 8 cycles per minute (0.08 - 0.13 Hz) correlated inversely with the levels of glycated hemoglobin (HbA 1c ) (r = - 0.56, p = 0.005) only in type 1 diabetic patients. In conclusion, we found suprasystolic occlusion and increasing blood pressure to provoke vasomotion with a concomitant decrease in effective vascular resistance only in type 1 diabetic patients. The impaired vasomotion response to shear stress in type 2 diabetes might favour the development of skin lesions and arterial hypertension. Insufficient glycemic control seems to be an important factor in the pathogenesis of impaired vasomotion in type 1 diabetes.