We have investigated the relationship between plasma endothelin (ET) concentrations and several clinical characteristics in 31 patients with acute myocardial infarction (MI). ET levels were also measured in 10 age-matched healthy subjects, 9 patients with unstable angina, and 20 patients with chronic heart disease. In patients with MI, although no significant relationship was observed between plasma ET concentrations and measured hemodynamic parameters, plasma levels were higher in patients with pulmonary congestion than in those without this complication (1.61 +/- 0.29 vs 1.21 +/- 0.33 fmol/ml; p < 0.01). No significant difference in plasma ET levels was found between cardiac and peripheral sampling sites (pulmonary artery; 1.07 +/- 0.28, right atrium; 1.02 +/- 0.28, peripheral artery; 1.12 +/- 0.23, peripheral vein; 1.14 +/- 0.38 fmol/ml: N.S.), or among patients with uncomplicated MI, unstable angina (1.00 +/- 0.32 fmol/ml), and healthy subjects (1.01 +/- 0.29 fmol/ml). Increased level were observed in patients with decompensated heart failure due to chronic heart disease, but were not found in patients without pulmonary congestion (1.62 +/- 0.60 vs 1.11 +/- fmol/ml; p < 0.01). These observations suggest that plasma ET concentrations are elevated in the presence of congestive heart failure or severe ventricular depression, but are not persistently increased by myocardial ischemia per se.