Studies using visceral (cardiovascular) autonomic function testing have left doubt as to the importance of autonomic neuropathy in the development of diabetic neuropathic foot ulceration. A test for peripheral autonomic denervation has been developed (acetylcholine sweatspot test), dependent on intradermal acetylcholine causing secretion by innervated sweat glands, detected by starch/iodine discoloration. The response is photographed and quantified using a grid (normal score = 0 or 1; abnormal = 5 to 60). The sweatspot test was applied to the feet of 19 diabetic patients with a history of foot ulceration, 17 with neuropathic pain, 8 complaining of numbness, and to 15 diabetic control patients. The sweatspot test score of the foot ulcer patients (median 54) was very much greater than that of the other groups (pain group, 4, p less than 0.005; numbness group, 2, p less than 0.01; diabetic control group, 2, p less than 0.0001). All the patients with neuropathic foot ulceration had peripheral autonomic denervation. The results suggest that autonomic denervation in the feet is always present in patients with diabetic neuropathic foot ulceration. Tests of peripheral autonomic denervation such as the acetylcholine sweatspot test may be useful to identify patients at risk of neuropathic foot ulceration.