Four non-steroid anti-inflammatory drugs, sulfinpyrazone, acetylsalicylic acid, sodium salicylate and indomethacin were tested in the acute phase of experimental myocardial infarction in conscious rats. A single oral dose was administered, then 1 h later the occlusion of the left anterior descending coronary artery was made by using a previously implanted silk loop. It was found that each drug markedly increased the survival rate, reduced the occurrence of ventricular fibrillation and tachycardia, and delayed the appearance and shortened the duration of arrhythmias.