Haemodynamic tests were performed at rest and during exercise in 41 patients with arterial hypertension and early impairment of left-ventricular function, before and after administration of a single dose of 0.6 mg beta-methyl-digoxin. After clinical, ECG and coronary-angiographic studies, the patients were assigned to two groups. Group I: 17 patients with transmural infarcts in the chronic stage or with angina. Cardiac output was within normal limits at rest and on exercise and was not significantly altered by administration of beta-methyl-digoxin. There was no significant fall during exercise of the abnormally elevated pulmonary "wedge" pressure or of other pressures in the lesser circulation after digitalis. Group II: 24 patients without signs of coronary heart disease. They, too, had a normal cardiac output at rest and on exercise, not significantly changed by digitalisation with beta-methyl-digoxin. But pulmonary "wedge" pressure and right-atrial mean pressure were significantly reduced during exercise. Before beta-methyl-digoxin the mean "wedge" pressure rose on exercise to an average of 27.3 +/- 5.4 mm Hg, but after beta-methyl-digoxin to only 21.7 +/- 5.1 mm Hg (P less than 0.001). The mean right atrial pressure changed similar. These results indicate that acute digitalisation at the stated dosage in general has an effect on abnormal myocardial function only if there is no additional coronary heart disease.