The impact of secondary prevention initiatives on survival in higher-risk socioeconomically disadvantaged patients after acute myocardial infarction (AMI) may depend on behavioral adaptive responsiveness, uptake, and adherence to healthier lifestyles. From December 1999 to February 2003, 1,801 patients in Ontario, Canada were interviewed regarding their lifestyle behaviors at 30 days after their index AMI hospitalization. Data were obtained using self-reported surveys, medical chart abstraction, and administrative data linkage. Multivariate analyses were adjusted for baseline sociodemographic, cardiac risk severity, and co-morbid conditions. Socioeconomically disadvantaged patients had greater cardiac risk severity at baseline than did their wealthier better-educated counterparts. Compared with lower-income patients, patients with higher incomes were less likely to smoke (adjusted odds ratio [OR] for highest vs lowest income tertiles 0.36, 95% confidence interval [CI] 0.21 to 0.63, p <0.001), more likely to participate in exercise (adjusted OR 1.40, 95% CI 1.07 to 1.85, p = 0.02), and more likely to decrease or discontinue alcohol use (adjusted OR 1.64, 95% CI 1.16 to 2.34, p = 0.06). The relation between education and lifestyle behaviors was less pronounced for education than for income. After adjustment for baseline factors, patients who acknowledged participation in regular physical exercise at 1 month had a significantly lower long-term mortality than those who did not. In conclusion, socioeconomically disadvantaged patients were sicker at baseline and less behaviorally responsive to embarking on healthy lifestyle changes after AMI than were those of higher socioeconomic status.