Oxygen-transporting function of the blood was studied in 137 patients in the early period of acute poisoning. Four groups of disorders of this function were distinguished: elevated oxygen consumption in parallel with high oxygen transport; increased oxygen consumption at normal oxygen transport; low oxygen consumption at low oxygen transport and increased coefficient of oxygen extraction by tissues; and low oxygen consumption in parallel with low oxygen transport without compensation. An integral index of oxygen transport efficacy is pvO2. A low pvO2 may be observed in case of inadequate delivery of O2 with the requirement in oxygen increasing. Normal or increased pvO2 at low oxygen consumption and transport may occur both during decreased requirement in O2 and in low cardiac output and centralized circulation. Heart productivity is mainly responsible for the compensation of reduced O2 content in the arterial blood.