Immense therapeutic effort has been devoted to testing the secondary preventative value of beta-blocking drugs in survivors of acute myocardial infarction. The failure to demonstrate a universally statistically significant benefit is ascribable to major inadequacies of design and technical errors in the majority of trials. Moreover, even in the very few trials in which survival benefit has been demonstrated, the ultra-selection of patients eventually included severely limits the general clinical application of their result. The specific subgroups of patients who derive most benefit and as importantly those that are disadvantaged by these drugs are ill-defined. Lack of comparative trials and absence of dose-response information also pose insuperable problems in attempting secondary prevention with beta-blocking drugs in practice. When to start these drugs to achieve maximum benefit and when to stop them to avoid long-term adverse reactions are major outstanding problems. The consequences of missed therapy are also unknown. Lack of a clinically discernible endpoint of success in the individual patient means that the physician's role is relegated to one of faith. Data so for available is insufficient to afford a rational change in therapeutic practice. However, these extensive studies have advanced understanding. They have clearly defined the design faults which must be avoided in future trials. They have made us aware that many post-infarct patients may not need beta-blocking drugs.(ABSTRACT TRUNCATED AT 250 WORDS)