Lung capacity to regulate the level of plasma prostanoids at the expense of their destruction or extra synthesis is one of their numerous non-gas-exchange functions. Prostaglandins A, E, and F, prostacyclin, and thromboxane were measured in the arterial and venous blood of 23 patients before and after surgery. The level of prostanoids was sharply increased in surgical patients. Substrates with the broncho- and vasoconstrictive action predominate in the blood of patients with obstructive and restrictive changes in the lungs, this eventually leading to complications in the postoperative period.