Blind drug trial in patients with an enzyme-documented acute myocardial infarction who were admitted to a coronary care facility. Data for living alone and/or a marital disruption were entered into a Cox proportional hazards model constructed from important physiologic and nonphysiologic factors in the same database. Setting.\p=m-\Multicenter trial in a mixture of community and academic hospitals in the United States and Canada. Patients.\p=m-\Allconsenting patients who were 25 to 75 years of age and without other serious diseases were enrolled (placebo, N = 1234) within 3 to 15 days of the index infarction and followed for a period of 1 to 4 years (mean, 2.1 years). Nine hundred sixty-seven patients were followed for 1.1 years and 530 for 2.2 years. Primary Outcome Measure.\p=m-\Recurrentmajor cardiac event (either recurrent nonfatal infarction or cardiac death). Results.\p=m-\Living alone was an independent risk factor, with a hazard ratio of 1.54 (95% confidence interval, 1.04 to 2.29; P<.03). Using the Kaplan-Meier statistical method for calculation, the recurrent cardiac event rate at 6 months was 15.8% in the group living alone vs 8.8% in the group not living alone. Risk remained signif- icant throughout the follow-up period (P=.001). A disrupted marriage was not an independent risk factor. Conclusion.\p=m-\Livingalone but not a disrupted marriage is an independent risk factor for prognosis after myocardial infarction when compared with all other known risk factors.