Risk of myocardial infarction and death during treatment with low dose aspirin and intravenous heparin in men with unstable coronary artery disease. The RISC Group 796 men with unstable coronary artery disease (unstable angina or non-Q-wave myocardial infarction [MI] ), were randomised to double-blind placebo-controlled treatment with oral aspirin 75 mg/day and/or 5 days of intermittent intravenous heparin. The risk of MI and death was reduced by aspirin. After 5 days the risk ratio was 0.43 (confidence intervals, 0.21-0.91), at 1 month 0.31 (0.18-0.53), and at 3 months 0.36 (0.23-0.57). Aspirin reduced event rate in non-Q-wave MI and unstable angina, independently of electrocardiographic abnormalities or concurrent drug therapy. Heparin had no significant influence on event rate, although the group treated with aspirin and heparin had the lowest number of events during the initial 5 days. Treatment had few side-effects and high patient compliance. 