In anesthetized dogs, i. v. injections of 0.1-1.0 mcg/kg adrenaline, noradrenaline, and isadrine evoked a raise of blood pressure in the right ventricle of the hear by 13-200%. The greatest pressor effects were obtained with isadrine, the smallest those--with noradrenaline. In experiments with closed chest animals with perfusion of lungs lobe by venous blood under constant pressure and recording of blood flow with photoelectric drop recorder, injections into perfusate of 0.02-32.0 mcg adrenaline and noradrenaline diminished blood flow and increased vascular resistance. In 1/3 of cases isadrine evoked the same reaction, in other cases it increased blood flow in perfused lobe and decreased resistance. The isadrine effect was blocked by beta--blocking agent inderal, whereas those of adrenaline and noradrenaline--by alpha-blocking drug phentolamine. Adrenaline and noradrenaline to constrict the pulmonary vessels by activating the vascular alpha-adrenoreceptors. Isadrine can dilate and constrict the lung vessels. In intact circulation isadrine seems to cause vasoconstriction and elevate blood pressure in lesser circulation.