Although the mass of data which have collected over the past 30 years on antithrombotic therapy following myocardial infarction have not provided conclusive results, there is greater cause for optimism than might be appreciated. We are becoming much better at designing and carrying out the largescale clinical trials necessary for a valid assessment of these drugs. We have come a long way from the early uncontrolled studies which led to triumphant conclusions, or even from the first small controlled studies consisting of only a hundred or so patients. Knowledge has been gained on the pitfalls of clinical trials, problems of patient selection, compliance, investigator bias, drop-outs and analysis of results. Experts may argue about the ways in which these problems should be overcome but at least there is awareness that there are problems. We now need a careful re-appraisal of several of the drugs already available, such as the oral anticoagulants. Also, properly designed studies are required to evaluate the new contenders in this field. We need patience, as well as finance, because the new trials will require large numbers of patients who must be followed-up for a sufficient length of time for valid end-points to emerge. Only when this type of trial has been carried out will the successful antithrombotic drugs be distinguished from their ineffective or toxic couterparts. In particular, trials must be capable of distinguishing between the alternative possibilities of a small treatment effect and no treatment effect (Peto, 1978). If a small but significant treatment effect is present, clinicians must then decide whether the advantages outweigh potential disadvantages such as toxicity of treatment, complicated dose regimens or difficult laboratory control. The attraction of the antiplatelet agents over oral anticoagulants or fibrinolytic therapy is their ease of administration and lack of haemorrhagic side effects, but we need firm and reproducible data on their efficacy before recommending their widespread use. In the meantime the protagonists of anticoagulant and fibrinolytic therapy have both made a strong case to have their drugs re-evaluated, and perhaps, in the future, we may have to consider whether combination therapy (say, a fibrinolytic drug for the acute stage of the disease followed by an antiplatelet agent for secondary prevention) is more effective than a single treatment alone.