Certificate of need laws provide state-level regulation of health system expenditure. These laws are intended to limit spending and control hospital expansion in order to prevent excess capacity and improve quality of care. Several states have recently introduced legislation to modify or repeal these regulations, as encouraged by executive order 13813, issued in October 2017 by the Trump administration.To evaluate the difference in markers of hospital activity and quality by state certificate of need status. These markers include hospital procedural volume, hospital market share, county-level procedures per 10 000 persons, and patient-level postoperative outcomes.A cross-sectional study involving Medicare beneficiaries aged 65 years or older who underwent 1 of the following 10 procedures from January 1, 2016, through November 30, 2018: total knee or hip arthroplasty, coronary artery bypass grafting, colectomy, ventral hernia repair, lower extremity vascular bypass, lung resection, pancreatic resection, cystectomy, or esophagectomy.State certificate of need regulation status as determined by data from the National Conference of State Legislatures.Outcomes of interest included hospital procedural volume; hospital market share (range, 0-1; reflecting 0%-100% of market share); county-level procedures per 10 000 persons; and patient-level postoperative 30-day mortality, surgical site infection, and readmission.A total of 1 545 952 patients (58.0% women; median age 72 years; interquartile range, 68-77 years) at 3631 hospitals underwent 1 of the 10 operations. Of these patients, 468 236 (30.3%) underwent procedures in the 15 states without certificate of need regulations and 1 077 716 (69.7%) in the 35 states with certificate of need regulations. The total number of procedures ranged between 729 855 total knee arthroplasties (47.21%) and 4558 esophagectomies (0.29%). When comparing states without vs with certificate of need regulations, there were no significant differences in overall hospital procedural volume (median hospital procedure volume, 241 vs 272 operations per hospital for 3 years; absolute difference, 31; 95% CI, -27.64 to 89.64; P = .30). There were no statistically significant differences between states without vs with certificate of need regulations for median hospital market share (median, 28% vs 52%; absolute difference, 24%; 95% CI, -5% to 55%; P = .11); procedure rates per 10 000 Medicare-eligible population (median, 239.23 vs 205.41 operations per Medicare-eligible population in 3 years; absolute difference, 33.82; 95% CI, -84.08 to 16.43; P = .19); or 30-day mortality (1.17% vs 1.33%, odds ratio [OR], 1.04; 95% CI, 0.93 to 1.16; P = .52), surgical site infection (1.24% vs 1.25%; OR, 0.93; 95% CI, 0.83 to 1.04; P = .21), or readmission rate (9.69% vs 8.40%; OR, 0.80; 95% CI, 0.57 to 1.12; P = .19).Among Medicare beneficiaries who underwent a range of surgical procedures from 2016 through 2018, there were no significant differences in markers of hospital volume or quality between states without vs with certificate of need laws. Policy makers should consider reevaluating whether the current approach to certificate of need regulation is achieving the intended objectives and whether those objectives should be updated.