IMPORTANCE The Hospital Readmissions Reduction Program (HRRP) was recently expanded to penalize excessive readmissions after total hip arthroplasty (THA) and total knee arthroplasty (TKA). These are the first surgical procedures to be included in the HRRP. OBJECTIVE To determine whether the HRRP was associated with a greater decrease in readmissions after targeted procedures (THA and TKA) compared with similar nontargeted procedures (lumbar spine fusion and laminectomy). DESIGN, SETTING, AND PARTICIPANTS A retrospective cohort study was conducted of patients 50 years or older among all payers in the Nationwide Readmissions Database who underwent THA, TKA, lumbar spine fusion, or laminectomy between January 1, 2010, and September 30, 2015. Multivariable logistic regression and interrupted time-series models were used to calculate and compare 30-day readmission trends in 3 periods associated with the HRRP: Preimplementation (January 2010-September 2012), implementation (October 2012-September 2014), and penalty (October 2014-September 2015). Statistical analysis was performed from January 1, 2010, to September 30, 2015. EXPOSURES Announcement and implementation of the HRRP. MAIN OUTCOMES AND MEASURES Readmission within 30 days after hospitalization for THA, TKA, lumbar spine fusion, or laminectomy surgery. RESULTS The study included 6 687 077 (58.3%women and 41.7%men; mean age, 66.7 years; 95% CI, 66.7-66.8 years) weighted hospitalizations for THA, TKA, lumbar spine fusion, and laminectomy surgery: 4 765 466 hospitalizations for targeted conditions and 1 921 611 for nontargeted conditions. After passage of the Patient Protection and Affordable Care Act, the risk-adjusted rates of readmission after all procedures decreased in a similar fashion. Implementation of the HRRP was associated with a 0.018%per month decrease in the rate of readmission (95%CI, -0.025%to -0.010%) after targeted procedures, which was not observed after nontargeted procedures (slope per month, -0.003%; 95%CI, -0.016%to 0.010%). Penalties were not associated with a greater decrease in readmission for either targeted or nontargeted procedures. CONCLUSIONS AND RELEVANCE These results appear to be consistent with hospitals responding to the future possibility of penalties by reducing readmissions after surgical procedures targeted by the HRRP.