In a multicentre double-blind randomised study comparing the effects of sulphinpyrazone 400 mg twice daily with those of placebo in patients after myocardial infarction 727 patients (365 on sulphinpyrazone, 362 on placebo) were enrolled and followed up for 12-48 months (mean 19.2). Treatment began 15-25 days after infarction. There were 49 reinfarctions (9 fatal, 40 nonfatal)-34 occurred in the placebo group and 15 in the sulphinpyrazone group, a reduction of 56%. In addition, a significant reduction of thromboembolic events was noted. It is concluded that sulphinpyrazone is effective in the prevention of reinfarction in patients surviving a recent myocardial infarction.