The aim of the present investigation was to study the effects of a single 100-micrograms i.v. administration of the synthetic heptadecapeptide [beta-Ala1-Lys17]ACTH1-17-4-amino-N-butylamide (ACTH 1-17) on the left ventricular performance. The systolic time intervals (STI) were recorded in 20 healthy adult young subjects (10 treated with ACTH 1-17 and 10 receiving placebo) before as well as 20, 40, 60 and 80 min after the i.v. ACTH 1-17 or placebo infusion. The STI were recorded immediately after blood withdrawal for measuring cortisol, aldosterone, adrenaline and noradrenaline plasma levels. A highly significant statistical difference was demonstrated for preejection period (PEP) and preejection period/left ventricular ejection time (PEP/LVET) ratio between subjects treated with ACTH 1-17 and subjects receiving placebo. As expected, a significant increase of cortisol and aldosterone plasma levels was observed in subjects treated with ACTH 1-17. The difference of adrenaline and noradrenaline plasma levels was statistically highly significant between subjects treated with ACTH 1-17 and those receiving placebo. The lack of increase in PEP and PEP/LVET ratio recorded in subjects treated with ACTH 1-17 is consistent with an increased left ventricular contractile performance. An increased plasma catecholamine release is postulated as the mechanism of this improvement.