The aim of this study was to investigate the haemodynamic effects of amrinone in patients with pulmonary hypertension and impaired right ventricular function. Twelve patients with mitral stenosis (NYHA classification III and IV) took part in the study. The haemodynamic measurements were performed in the steady state under anaesthesia prior to surgery. The patients received a bolus injection of 1.5 mg kg-1 amrinone; haemodynamic measurements were taken at 3, 5, 10, 15, 20 and 30 min. Amrinone increased cardiac index by approximately 30%, heart rate rose from on average 76 to 82 beats per minute. Whereas pulmonary capillary pressure did not change significantly, mean pulmonary artery pressure fell clearly from 33 to 28 mmHg. A decrease in the elevated pulmonary vascular resistance of about 40% was calculated. The higher the initial value for resistance in the pulmonary circulatory system, the more marked was the reduction (r = 0.96). The study shows that amrinone induces a vasodilation in the pulmonary circulatory system. A reduction in ventricular afterload is of great significance particularly for the therapy of right heart insufficiency. Amrinone therefore appears to be a suitable substance with its observed vasodilating and its well known positive inotropic effects for the treatment of right heart failure in cases of pulmonary hypertension.