Angiotensin converting enzyme (ACE) inhibitors are effective across the whole spectrum of heart failure from mild to severe hut there are little data on the use of ACE inhibitors specifically in patients with postinfarct heart failure. Pharmacological properties that might potentially be relevant to the choice of drug after myocardial infarction include differences in metabolism, possession of a sulphydryl group, tissue binding, duration of action, and side effect profile. Of these duration of action is probably the most important, as longer acting drugs generally cause more prolonged first-dose hypotension than shorter acting agents and first-dose hypotension is a particular concern in the early postinfarct period. In the SAVE study captopril was effective in reducing mortality and delaying the onset of symptomatic heart failure after myocardial infarction. Similarly, ramipril reduced mortality in the AIRE study. In contrast, enalapril was largely ineffective in CONSENSUS II. These differences result largely from study design and do not indicate an inherent superiority of captopril or ramipril over enalapril. Nonetheless, a short-acting agent should probably be used for the initial dose in postinfarct heart failure to minimize the risks of prolonged hypotension. This aside, the choice of agent is far less important than appropriate patient selection and appropriate maintenance dosages.