Background: Athero-thrombotic events are common among patients with heart failure but there is no evidence that anti-thrombotic therapy is safe or effective in this clinical setting. Aims and Methods: The WASH study is a prospective, randomised, open-label, blinded-end-point pilot study comparing the outcome of management without anti-thrombotic therapy compared to treatment with aspirin or warfarin in three parallel arms in patients with chronic heart failure due to left ventricular systolic dysfunction. The primary aim of the study is to assess the feasibility of conducting a large study in which one-third of patients would be randomised to no anti-thrombotic therapy. The principal secondary aim of the study is to compare the effects of treatment on the combined end-point of death, non-fatal myocardial infarction and non-fatal stroke. Results: 279 patients have been randomised and by study close there wl~re 626 patient-years of follow-up. The majority of patients randomised had heart failure secondary to coronary artery disease. We expect to commence data analysis in early 1999 and report later in that year. Conclusions: This pilot study demonstrated that it is technically feasible to conduct a study that included a no anti-thrombotic treatment arm but that recruitment to such a study would be slow and costly. A large trial comparing the effects of aspirin, warfarin and clopidogrel in three separatl~ groups without a placebo arm is now intended.