It is uncertain whether anti-thrombotic treatment reduces the incidence of thrombo-embolism in patients with heart failure, so there is a need for a large scale controlled study to assess the effects of anti-thrombotic therapy in this setting. We report the design of a randomized controlled multicenter double blind trial examining the effects of aspirin, warfarin and placebo in patients with heart failure on the risk of thrombo-embolism. We planned to recruit 6000 patients with heart failure without contraindications to anticoagulants or antiplatelet agents and to follow them for a mean time of 2 years following randomization. The study was planned to determine the rate of thrombo-embolic and haemorrhagic events and death among patients randomized to aspirin, warfarin and placebo, stratified according to the presence or absence of underlying coronary disease. Ancillary studies parallel to the main study will attempt to identify clinical and echocardiographic risk factors for thrombo-embolism and will also examine whether hemostatic or neurohormonal mechanisms contribute to an increase in the risk of thrombo-embolism in patients with heart failure. We hoped that the results of the study would improve the clinical management and cost-effectiveness of treatment for patients with heart failure. However, the recruitment of patients proved more difficult than expected and a number of centers decided not to participate. To avoid a great delay it was decided by the principal investigators and submitted to the executive committee to terminate enrolment in this study when 300 patients had been enrolled, and accept that this is a pilot study.