We investigated possible differences over time in underlying causes of death among validated definite myocardial infarction cases who were discharged following an index hospitalization in 1970, 1980, and 1985 in the Twin Cities, MN. No changes were observed in underlying causes of death assigned to patients who died prior to discharge in the 3 years. Among in-hospital survivors of definite MI, however, age-adjusted rates of death from non-cardiovascular causes more than doubled between 1970 and 1985 (P < 0.01). More specifically, mortality rates for diabetes mellitus increased significantly from 1970 to 1985 (P < 0.05), while those for neoplasms and diseases of the respiratory system increased non-significantly. Whether these data are the result of artifactual changes in cause of death assignment or real changes in disease severity and comorbidity, these trends in long-term death following acute MI may have had a modest impact on reported community-wide coronary heart disease mortality rates.