Neither of the co-primary outcomes was significantly reduced by allocation to metoprolol. For the primary composite outcome of death, reinfarction, or cardiac arrest, 2166 (9.4%) patients had at least one such event among the 22 929 allocated metoprolol compared with 2261 (9.9%) among the 22 923 allocated matching placebo (odds ratio [OR] 0.96 [95% CI 0.90-1.01]; p=0.1). For the co-primary outcome of death alone, there were 1774 (7.7%) in the metoprolol group versus 1797 (7.8%) in the placebo group (OR 0.99 [0.92-1.05]; p=0.69). Allocation to metoprolol was associated with 5 fewer people having reinfarction (464 [2.0%] metoprolol vs 568 [2.5%] placebo; OR 0.82 [0.72-0.92]; p=0.001) and 5 fewer having ventricular fibrillation (581 [2.5%] vs 698 [3.0%]; OR 0.83 [0.75-0.93]; p=0.001) per 1000 treated. Overall, these reductions were counter-balanced by 11 more per 1000 allocated metoprolol developing cardiogenic shock (1141 [5.0%] vs 885 [3.9%]; OR 1.30 [1.19-1.41]; p<0.00001). The excess of cardiogenic shock was chiefly during days 0-1 after hospitalisation, whereas the reductions in reinfarction and ventricular fibrillation emerged more gradually. Consequently, the overall effect on death, reinfarction, arrest or shock was significantly adverse during days 0-1 and significantly beneficial thereafter. There was substantial net hazard among haemodynamically unstable patients and moderate net benefit among those who were relatively stable, particularly after days 0-1.