A double blind randomised study of 154 patients with myocardial infarction assigned to metoprolol (100 mg twice daily) and 147 assigned to placebo compared the effects of treatment in relation to health state over three years. Health state was evaluated by a new method based on the average number of days spent in each of seven mutually exclusive categories of health. The scale took into account death, history of serious complications, functional state, and side effects of treatment. Of the maximum attainable 1095 days alive during the three years patients given metoprolol attained 992 days and those given placebo 964 days. During the period alive the metoprolol treated group spent an average of 278 days in an optimal functional state as compared with 176 days for the placebo treated group. This included 221 and 156 days respectively in a completely asymptomatic state (that is, without either cardiac symptoms or side effects of treatment). The time spent with a serious non-fatal complication was shortened by 56 days in the metoprolol group. The overall differences between the groups were statistically significant (p = 0.03). Aside from bringing an improved quality of life after myocardial infarction, metoprolol may add up to one month to life expectancy for three years of treatment.