vestigations were performed during 24 simulated air dives under pressure 0.74 MPa in which 16 divers took part. Before, during and after dives intrathoracic pressure, mean arterial pressure, ECG, rheoplethysmogram and intervalocardiogram were recorded continuously with the Valsalva maneuvers. Variables of heart pumping function, peripheral vascular system, phasic heart cycle structure were calculated. For evaluation of autonomic homeostasis variational and spectral analysis of cardiac rhythm were used. In hyperbaria a part of hemodynamic response peculiarities to intrathoracic pressure increase were common to all divers and caused by hyperoxia and increased density of breathing medium, which lead to the appearance of bradycardia, decrease of cardiac output, peripheral vasoconstriction enhancement. Other observed features were determined by alterations in sympathetic and parasympathetic nervous system tonus. These changes were rather complex and highly individual. Our data may benefit evaluation of hyperbaric factor stressful action on blood flow and autonomic nervous system.