The effect of nitroglycerin, methoxamine, and the combination of both drugs were studied in anaesthetized dogs, during the acute phase of experimental myocardial infarction. Different haemodynamic and electrophysiological parameters were measured during the first three minutes of occluding the left descending coronary artery, while each drug or the combination were being infused. After stopping infusions, new occlusions were performed periodically in order to assess the persistence of drug effects. Nitroglycerin alone provoked hypotension and reduced the development of the ischaemic area, while methoxamine did not modify the measured variables. A long-lasting favourable effect on the ischaemic area was recorded when methoxamine prevented hypotension induced by nitroglycerin.