The purpose of this study was to evaluate the ability of beta blocker therapy in decreasing the amount of necrosis during a first transmural myocardial infarction (as evidenced by a local and overall kinetic study using two-dimensional ultrasonography). Twenty patients were randomly placed into 2 groups. Ten patients received 15 mg of metoprolol intravenously followed by 200 mg daily of the drug orally. The results indicated that beta blockers are well tolerated clinically and hemodynamically, and that they significantly reduced the amount of necrosis (p less than 0.05 in anterior myocardial infarctions).