Phentolamine (Regitine) at the dose of 0.3 mg/mn behaves as an arterial and, above all venous, vasodilatator agent, resulting in a marked and early lowering of the pulmonary pressures in acute oedema of the lung and in cardiac asthma. It was used alone in 47 attacks of acute severe left ventricular failure with very favourable results in 43 cases, as proved by the rapid improvement of the haemodynamic status and of the aicd-base balance. Under strict observation, tolerance has been excellent. This therapeutic method seems of great interest in the cases of acute pulmonary oedema with a maintained blood pressure level, and in the forms with severe arterial hypertension which might tolerate larger doses.