BACKGROUND: Insufficient nocturnal blood pressure (BP) decline is associated with elevated risk of complications of hypertensive disease. Heart rate variability (HRV) reflects activity of sympathetic and parasympathetic parts of autonomic nervous system. AIM: To elucidate special characteristics of HRV in patients with various types of 24-hour BP rhythm. Material and methods. Bifunctional 24-hour monitoring and echocardiography were carried out in 42 men with stage I-II hypertensive disease and I-II degree of arterial hypertension (mean age 21.7+/-4.5 years) and 16 practically healthy young people (mean age 24.6+/-5.2 years). RESULTS: Subjects with insufficient (<10%) and adequate nocturnal BP decline (non-dippers and dippers) were distinguished (groups ND and D, respectively). Patients with hypertension in group ND had elevation of systolic BP variability during night and day time, augmentation of nocturnal and diurnal HRV low frequency power, lowering of nocturnal high frequency power, lowering of pNN50 and rMSSD values at night. HRV parameters of control subjects in this group did not differ from those of healthy people. All HRV parameters in group D were characterized by significant 24-hour rhythmicity. This rhythmicity was substantially disturbed in patients of group ND. Parameters of central hemodynamics were similar in groups D and ND. CONCLUSION: These results evidence for the presence of enhanced activity of sympathetic part of autonomic nervous system in non-dipper patients with hypertensive disease throughout 24 hours and during night time and for disturbed circadian rhythm of autonomic nervous system activity. This can serve as a basis for increased rate of cardiovascular complications in this category of patients.