A team of Mathematica researchers reviewed data from a survey of 800 primary care practices and found that most of them—including practices participating in the Comprehensive Primary Care (CPC) initiative—dismissed an average of between one and 20 patients over a two-year period. The number of dismissed patients was proportional to the size of the practice. Common reasons for dismissing a patient included disruptive behavior, violating policies on chronic pain medicines and controlled substances, or repeatedly missing appointments. Notably, participating in CPC had no effect on whether patients were dismissed, and in some cases it made practices less likely to dismiss patients. These findings are especially relevant to patients, payers, and policymakers, because there is a perception that as insurers shift from volume-based to value-based reimbursements, physicians may consider this an incentive to limit their practice to those patients for whom they can readily demonstrate value in order to maximize revenue.