The effect of prostaglanding B1 (PGB1) on the cardiovascular system of dogs was studied in experiments on anesthetized dogs. The intravenous injection of PGB1 (40 microng/kg) was followed by aortic hypertension, tachycardia, an increase of myocardial contractility, an enhancement of minute volume of the heart, and in increase of arterial pressure in the pulmonary artery. Total peripheral resistance and total lung resistance were reduced. The work of the left and the right ventricles and the coronary flow increased (the latter by 29%). The average voluminous blood flow velocity in the femoral and the superior mesenteric arteries increased significantly, while in the common carotid and the renal arteries--insignificantly. The observed changes in the systemic and regional hemodynamics were of short duration.