Comparable groups of diabetic patients asymptomatic of neuropathy (Group A), with chronic painful polyneuropathy (Group B) and painless polyneuropathy causing recurrent foot ulceration (Group C) were studied for differences in pedal blood flow, peripheral somatic and autonomic neuropathy and vascular calcification. Blood flow abnormalities detected by doppler waveform analysis, and consistent with reduced peripheral vascular resistance, were found in all three diabetic patient groups. The abnormalities were of similar severity in Group A and B but generally more marked in Group C. Tests of peripheral somatic nerve function became progressively more abnormal from Group A to Group C. Autonomic neuropathy was equally severe in Groups B and C, although mild abnormalities were recorded in diabetic patients asymptomatic of neuropathy. A similar pattern was seen for vascular calcification in the tarsal and metatarsal arteries: marked in both neuropathic groups (B and C) but mild in Group A. It was concluded that abnormal blood flow consistent with reduced peripheral vascular resistance is very common in the feet of diabetic patients whether or not they are symptomatic of neuropathy, and is most severe in those with chronic painless polyneuropathy and recurrent foot ulceration. No clear relationship was found between autonomic nerve dysfunction and the degree of abnormality of blood flow.