Thirty-one diabetic subjects, 19 males and 12 females, with a mean age of 40.5 +/- 14.0 years, 17 of whom were insulin dependent (IDDM) and 14 non-insulin dependent (NIDDM) treated with insulin and diet, were followed for a period of six months. Patients were diagnosed of diabetic autonomic cardiopathy (without other neuropathy causes, nor use of drugs except for insulin) by the alteration of at least 2 of the 5 cardiovascular tests (tCV) performed. Patients underwent an educational diabetes program and self-control, and after 6 months of treatment they were divided into two groups according to the degree of metabolic control. In group 1, in which there was a good control with mean blood sugar levels of 108 +/- 12 mg/dl (5.9 +/- 0.6 mmol/l) and triglycerides of 101 +/- 21 (1.1 +/- 0.2 mmol/l), an improvement in tCV was observed: Valsalva coefficient of 1.16 +/- 0.13 and 1.22 +/- 0.13 (initial and final respectively) (p less than 0.001), with and improvement in 56% of cases; E/I (expiration/inspiration) ratio increased from 1.13 +/- 0.11 to 1.21 +/- 0.11, improving 53% of cases (p less than 0.001); 30/50 index (RR in 30/RR beat in beat 15 after orthostatism) (n.s.); difference in systolic arterial pressure after standing (p less than 0.001) and increase in diastolic arterial pressure with isometric muscular exercise (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)