An increasing number of ACE inhibitors have become available in recent years. Because these agents are all similar, careful scrutiny is required in order to determine specific advantages of particular agents when making formulary decisions. Differences between agents with regard to structure and tissue specificity have been identified, but the clinical relevance of these differences is not clear. ACE inhibitors vary greatly with regard to bioconversion, distribution and elimination. Disease states such as congestive heart failure (CHF) and hepatic or renal insufficiency may affect the disposition of specific ACE inhibitors. These agents may differ substantially in duration of action, and ACE inhibitors that are given once daily may optimise patient compliance and decrease costs. ACE inhibitors have been extensively studied in patients with hypertension, CHF or nephropathy, and following myocardial infarction (MI). Differences in efficacy between agents are often a result of variations in study design, or because nonequipotent dosages were compared. It is likely that the benefits of ACE inhibitors are class effects, and it is probably reasonable to use an agent even if large scale clinical trials have not been performed with that particular drug. Few differences have been found between ACE inhibitors with regard to adverse effects or drug interactions, and these factors are of minor importance when making formulary decisions. Cost and availability may vary among agents, and will depend on geographical location and institution-specific purchasing contracts. ACE inhibitors have shown positive effects on quality of life when compared with agents of other classes. Quality-of-life studies that have directly compared ACE inhibitors have produced conflicting results. In the setting of hypertension, cost-effectiveness evaluations typically find that the newer, longer-acting ACE inhibitors provide the greatest financial benefit. Differences in cost effectiveness in the post-MI patient population are typically the result of variations in protocol design, including duration of treatment and nondrug costs. ACE inhibitors are fairly homogeneous and selection between agents can be difficult. Clinical efficacy, time course of action, and cost are the primary concerns in selecting agents for inclusion on a formulary.