This study aimed at evaluating vasomotor response of the hand in patients with diabetes mellitus. A skin temperature of the hand was measured before and after exposure to ice water, and the recovery rates of the skin temperature were determined at 3, 5, and 10 min after the cold exposure. Ninety-two diabetics ranging in age from 25 to 59 years and 43 normal subjects ranging from 23 to 69 years old participated in this study. Since the recovery rate was delayed in normal subjects over the age of 60, comparison was made between the diabetics and the normals under 60 years old. The skin temperature was significantly lower in 26 diabetics with severe peripheral neuropathy (PN) than 40 diabetics without PN. The recovery rate were markedly delayed in the patients with PN, and also delayed in diabetics with severe retinopathy. The recovery rate was not different between the patients with and without ischemic changes in electrocardiogram. The delayed recovery rate was most prominent in the diabetics who had both abnormal heart rate variation (HRV) and orthostatic hypotension, followed by those with abnormal HRV but without orthostatic hypotension. Recovery rates in the diabetics with abnormal HRV alone were within the normal range. Our data suggest that the dysfunction of the regulation of skin temperature in the patients with diabetes mellitus was due to peripheral sympathetic nerve abnormality. The cold exposure test would be useful in the estimation of the sympathetic nerve activity of the diabetics.