As part of an ongoing community-wide study of time trends in the incidence and case-fatality rates of patients hospitalized with acute myocardial infarction (MI) in all 16 Worcester, Massachusetts, metropolitan hospitals during the years 1975, 1978, 1981, and 1984, changes over time in the therapeutic management of 3263 patients with validated acute myocardial infarction were examined. Beta-blocker (21%, 1975; 52%, 1984) and nitrate (56%, 1975; 93%, 1984) therapy use increased dramatically over time. Use of antiplatelet agents was inconsistent over time, while use of digoxin remained stable, being used in approximately 40% of all patients over the four periods studied. Use of antiarrhythmic medications other than lidocaine decreased consistently over time (31%, 1975; 22%, 1984). Lidocaine use increased between 1975 (31%) and 1978 (52%) and then leveled off to being used in approximately 45% of hospitalized patients with acute MI in 1981 and 1984. A variety of demographic (e.g., age, sex, teaching hospital) and clinical characteristics (e.g., MI order, MI type, MI location, peak CPK findings, occurrence of acute clinical complications) were also associated with the use of these therapies for the combined study periods. The results of this population-based study suggest considerable changes over time in the therapeutic management of patients hospitalized with acute myocardial infarction and of numerous patient demographic and clinical factors associated with their use.