Doctors treat patients, not populations. 'Evidence-based' practice is essential but extrapolation to the individual patient is always necessary and this fact is well illustrated by data from trials of ACE inhibitors post-myocardial infarction. In the AIRE (Acute Infarction Ramipril Efficacy) study, 2,006 patients with some evidence of heart failure, even if transient, after a myocardial infarction, were randomised to receive oral ramipril or placebo in addition to standard treatment. Follow-up was for a minimum of six and an average of 15 months. The risk reduction in total mortality was 27% (95% CI 11-40%; p = 0.002); approximately 40 lives might be expected to be saved for every 1000 patients treated for one year. Benefit was apparent within weeks of starting treatment. Additional data from the AIRE study are considered in relation to the findings of other mortality trials. It is argued that ACE inhibitors offer most to those patients with impaired left ventricular function through a mechanism not related to the prevention of myocardial re-infarction.