Assessment of diabetic autonomic neuropathy in a representative sample of 91 noninsulin-dependent diabetics was performed in 3 community clinics. A difference of less than 10 beats/min in heart rate between deep inspiration and deep expiration determined by ECG recording served as the criterion for autonomic neuropathy. By this test, 86% of the patients had diabetic autonomic neuropathy, a slightly higher proportion than that reported by others using similar criteria in more selected populations. The test is very sensitive and can be used for screening.