Résumé : We compared the effects on hemodynamics and blood gases of an intravenous perfusion of diltiazem vs placebo, administered randomly and in a double-blind fashion, to 20 patients with acute myocardial infarction (<24 hours). After 130 minutes, we noted a significant reduction of the arterial blood pressure and the systemic vascular resistances; the other hemodynamic variable are not significantly modified. Diltiazem causes a slight but significant decrease of PaO2 after 130 minutes in intravenous perfusion. This effect is secondary to an increase of the arterio-alveolar gradient in O2, reflecting an increase of the pulmonary shunt. This has no clinical consequence since the oxygen transfer remains stable. In conclusion, intravenous diltiazem administered in the acute phase of myocardial infarction is well tolerated hemodynamically and clinically. It may induce a minimal arterial hypoxemia by increasing the arterio-alveolar gradient in oxygen.