The Fragmin and/or Early Revascularisation during Instability in Coronary Artery Disease (FRISC II) trial will, in a prospective multicenter factorially randomized study, compare the efficacy of 3 months continuation of subcutaneous treatment with the low-molecular-weight heparin dalteparin (Fragmin) with that of placebo and will also compare a direct invasive strategy with a stepwise selective approach with regard to the utilization of coronary angiography and revascularization in patients with unstable coronary artery disease. The primary endpoints are death or myocardial infarction after 3 and 6 months respectively. Secondary endpoints are the same events after 12-24 months and also cardiac symptoms, exercise capacity, and/or signs of myocardial ischemia, readmission, and costs. Analyses will also be made of subgroups based on inclusion diagnosis, initial elevation of biochemical markers of myocardial damage, elevation of fibrinogen or C-reactive protein, signs of ischemia in electrocardiography at rest or at continuous 24-hour ischemia monitoring, and left ventricular function at echocardiography. Altogether, 3,100 patients will be recruited in 65-70 Scandinavian centers. Completion of follow-up is anticipated in the second half of 1998. The FRISC II study will further elucidate new alternatives for antithrombotic, invasive, and individually tailored treatment of unstable coronary syndromes.