We analyzed the costs and effectiveness of routine therapy with beta-adrenergic antagonists in patients who survived an acute myocardial infarction. On the basis of data pooled from the literature, this form of therapy resulted in a 25 percent relative reduction annually in the mortality rate for years 1 to 3 and a 7 percent relative reduction for years 4 to 6 after a myocardial infarction. The estimated cost of six years of routine beta-adrenergic-antagonist therapy to save an additional year of life was $23,400 in low-risk patients, $5,900 in medium-risk patients, and $3,600 in high-risk patients, assuming that the entire benefit of earlier treatment is lost immediately after six years. Under a more likely assumption--that the benefit of six years of treatment wears off gradually over the subsequent nine years--the estimated cost of therapy per year of life saved would be $13,000 in low-risk patients, $3,600 in medium-risk patients, and $2,400 in high-risk patients. As compared with coronary-artery bypass grafting and the medical treatment of hypertension, routine beta-adrenergic-antagonist therapy has a relatively favorable cost-effectiveness ratio.