Background: In 2014, the American Board of Internal Medicine (ABIM) substantially increased the requirements and fees for its maintenance-of-certification (MOC) program. Faced with mounting criticism, the ABIM suspended certain content requirements in February 2015 but retained the increased fees and number of modules. An objective appraisal of the cost of MOC would help inform upcoming consultations about MOC reform. Objective: To estimate the total cost of the 2015 version of the MOC program ("2015 MOC") and the incremental cost relative to the 2013 version ("2013 MOC"). Design: Decision analytic model. Data Sources: Published literature. Target Population: All ABIM-certified U.S. physicians. Time Horizon: 10 years (2015 to 2024). Perspective: Societal. Intervention: 2015 MOC. Outcome Measures: Testing costs (ABIM fees) and time costs (monetary value of physician time). Results of Base-Case Analysis: Internists will incur an average of $23 607 (95% CI, $5380 to $66 383) in MOC costs over 10 years, ranging from $16 725 for general internists to $40 495 for hematologists-oncologists. Time costs account for 90% of MOC costs. Cumulatively, 2015 MOC will cost $5.7 billion over 10 years, $1.2 billion more than 2013 MOC. This includes $5.1 billion in time costs (resulting from 32.7 million physician-hours spent on MOC) and $561 million in testing costs. Results of Sensitivity Analysis: Costs are sensitive to time spent on MOC and MOC credits obtainable from current continuing education activities. Limitation: Precise estimates of time required for MOC are not available. Conclusion: The ABIM MOC program will generate considerable costs, predominantly due to demands on physician time. A rigorous evaluation of its effect on clinical and economic outcomes is warranted to balance potential gains in health care quality and efficiency against the high costs identified in this study.