The objective of the Beta-Blocker Pooling Project (BBPP) was to collect and analyse data from the major long-term secondary prevention trials in order to determine whether there are subsets of post-infarction patients who benefit to a greater or lesser extent from beta-blocker therapy than the average patient population. One-year all-cause mortality data from nine trials involving 13,679 patients were obtained. Overall, mortality was 24% lower in the beta-blocker group compared to the placebo group. However, there was heterogeneity among the results of the trials, which tested seven different beta-blockers. Subgroups with high placebo group mortality (e.g. patients with a history of previous myocardial infarction (MI), angina pectoris, mechanical or electrical complications, and digitalis usage) seemed to benefit particularly from beta-blocker treatment. These findings were consistent in the nine trials. Patients in the lower risk subgroups also appeared to benefit from beta-blockers, but this benefit was smaller in absolute terms and inconsistent across the trials. There was no evidence that treatment outcome was related to gender, baseline level of heart rate or blood pressure, or time of initiation of treatment after hospital admission. In conclusion, the Pooling Project indicates that high risk MI patients, without contraindications to beta-blockers, are the prime candidates for long-term therapy, but the lower risk patients may also receive some benefit.