The results of a randomized controlled trial of a single daily dose of acetyl salicylic acid (aspirin) in the prevention of reinfarction in 1,239 men who had had a recent myocardial infarct were statistically inconclusive. Nevertheless, they showed a reduction in total mortality of 12% at six months and 25% at twelve months after admission to the trial. Further trials are urgently required to establish whether or not this effect is real.