The growing size of trials on primary and secondary prevention of acute coronary syndromes characterised by very broad inclusion criteria may seem logical to 'trialists', who reason that the the broader the inclusion criteria, the easier it is to recruit large numbers of patients in a short period of time and the more widely applicable are the results of the study. However, large trials with very broad inclusion criteria raise two grounds for concern for physicians. The first is that the broader the inclusion criteria for enrollment in a trial in order to prove a statistically significant benefit, the greater the heterogeneity of the study population which is likely to include both susceptible and non-susceptible patients to the tested treatment. The second is that this method of assessment rapidly increases the number of treatments that produce a statistically-significant improvement in prognosis within the same broad group of patients. On the contrary, the identification of potential responders to a specific treatment can provide a personalised form of medical care suited to the needs of each individual patient with an optimal cost-benefit ratio. This approach, however, represents a major challenge as it can only be based on the identification of homogeneous subgroups of patients with common risk factors for the development of acute coronary syndromes or of their recurrence. This challenge can only be overcome by a strong commitment in funding studies on the multiple causes of acute coronary syndromes.