Background: Although beta-blockers are recommended following myocardial infarction (MI), the benefits of long-term treatment have not been established. The study's aim was to evaluate beta-blocker efficacy by dose in 1-year post-MI survivors. Methods and Results: The OBTAIN (Outcomes of Beta-Blocker Therapy After Myocardial Infarction) registry included 7057 patients with acute MI, with 6077 one-year survivors. For this landmark analysis, beta-blocker dose status was available in 3004 patients and analyzed by use (binary) and dose at 1 year after MI. Doses were classified as no beta-blocker and >0% to 12.5%, >12.5% to 25%, >25% to 50%, and >50% of target doses used in randomized clinical trials. Age was 63 to 64 years, and approximately two thirds were men. Median follow-up duration was 1.05 years (interquartile range, 0.98-1.22). When analyzed dichotomously, beta-blocker therapy was not associated with improved survival. When analyzed by dose, propensity score analysis showed significantly increased mortality in the no-beta-blocker group (hazard ratio,1.997; 95% CI, 1.118-3.568; P<0.02), the >0% to 12.5% group (hazard ratio, 1.817; 95% CI, 1.094-3.016; P<0.02), and the >25% to 50% group (hazard ratio, 1.764; 95% CI, 1.105-2.815; P<0.02), compared with the >12.5% to 25% dose group. The mortality in the full-dose group was not significantly higher (hazard ratio, 1.196; 95% CI, 0.687-2.083). In subgroup analyses, only history of congestive heart failure demonstrated significant interaction with beta-blocker effects on survival. Conclusions: This analysis suggests that patients treated with >12.5% to 25% of the target dose used in prior randomized clinical trials beyond 1 year after MI may have enhanced survival compared with no beta-blocker and other beta-blocker doses. A new paradigm for post-MI beta-blocker therapy is needed that addresses which patients should be treated, for how long, and at what dose.