Cardiovascular autonomic function is measured as heart rate variability (HRV). The aim of the study was the HRV comparison between type 1 diabetic patients without (R0) and with diabetic retinopathy (R1). The group R0 was significantly younger (36.08 +/- 13.52 years) than group R1 (42.90 +/- 10.42 years). Diabetes duration was significantly longer in the group R1 as compared to group R0 (22.60 +/- 8.72 years vs 16.72 +/- 11.54 years, p < 0.04). Also HbA1c level in the group R1 was significantly higher as compared to the group R0 (p = 0.006). The data demonstrated that abnormal HR variability measured over a 24-h period provides information on the risk of sudden death. To assess HR variability twenty four hour EKG monitoring were performed in all examined patients. RR intervals were significantly longer between 2.00 a.m. and 5.00 a.m. In each hour of 24-h EKG Holter monitoring VLF and LF were significantly lower in the group R1. In the group R1 - HF was also significantly lower but only during sleeping time (between 11 p.m. and 7 a.m.). 24-h EKG monitoring is a useful and promising tool in diabetic patients with different microvascular complications.