IMPORTANCE The US Centers for Medicare and Medicaid Services Hospital Readmissions Reduction Program penalizes hospitals with higher-than-expected risk-adjusted 30-day readmission rates (excess readmission ratio [ERR] > 1) after acutemyocardial infarction (MI). However, the association of ERR with MI care processes and outcomes are notwell established. OBJECTIVE To evaluate the association between ERR forMI with in-hospital process of care measures and 1-year clinical outcomes. DESIGN, SETTING, AND PARTICIPANTS Observational analysis of hospitalized patients with MI from National Cardiovascular Data Registry/Acute Coronary Treatment and Intervention Outcomes Network Registry-Get With the Guidelines centers subject to the first cycle of the Hospital Readmissions Reduction Program between July 1, 2008, and June 30, 2011. EXPOSURES The ERR forMI (MI-ERR) in 2011. MAIN OUTCOMES AND MEASURES Adherence to process of care measures during index hospitalization in the overall study population and risk of the composite outcome of mortality or all-cause readmission within 1 year of discharge and its individual components among participants with available Centers for Medicare and Medicaid Services-linked data. RESULTS The median ages of patients in the MI-ERR greater than 1 and tertiles 1, 2, and 3 of the MI-ERR greater than 1 groupswere 64, 63, 64, and 63 years, respectively. Among 380 hospitals that treated a total of 176 644 patients with MI during the study period, 43%had MI-ERR greater than 1. The proportions of patients of black race, those with heart failure signs at admission, and bleeding complications increased with higher MI-ERR. Therewas no significant association between adherence to MI performance measures and MI-ERR (adjusted odds ratio, 0.94; 95%CI, 0.81-1.08, per 0.1-unit increase in MI-ERR for overall defect-free care). Among the 51 453 patients with 1-year outcomes data available, higher MI-ERRwas associated with higher adjusted risk of the composite outcome and all-cause readmission within 1 year of discharge. This associationwas largely driven by readmissions early after discharge andwas not significant in landmark analyses beginning 30 days after discharge. The MI-ERRwas not associated with risk for mortality within 1 year of discharge in the overall and 30-day landmark analyses. CONCLUSIONS AND RELEVANCE During the first cycle of the Hospital Readmissions Reduction Program, participating hospitals' risk-adjusted 30-day readmission rates followingMI were not associated with in-hospital quality ofMI care or clinical outcomes occurring after the first 30 days after discharge.