The present study compares the protective effects of sodium selenite (Se), hyaluronidase (Hy) and anisodamine (An) on infarct size, left ventricular myocardial contractility (LVMC) and relaxation (LVMR) and myocardial hypertrophy on the 3rd, 9th and 21st days after the ligation of left main coronary artery in the rats. The results showed that Se could reduce the infarct size, so could Hy and An. However, Se could relevantly improve LVMC and LVMR at the acute phase of infarction, while Hy and An could not. On the 21st day (healing phase) of infarction the indexes of the LVMC and LVMR in Se-, Hy- or An-treated rats were significantly better than those in the control rats. Se could enhance the extent of hypertrophy in non-infarcted myocardium, while Hy and An could not. On the 21st day of this experiment the total natural mortality in the Se-treated rats was significantly lower than that in the control or in the An-treated rats. These data suggest that Se is superior to Hy and An in the treatment of acute myocardial infarction.