The chapters of this dissertation comprise two separate studies on topics related to physician behavior. Both chapters explore how physicians respond to state interventions to influence decision-making, with the goals of changing practice patterns and improving health outcomes. In first chapter, I investigate the effects of a value-based payment reform on physician behavior using Medicaid managed care claims data from Anthem, Inc. In 2015, Tennessee Medicaid transitioned all providers to a bundled payment model for episodes covering maternity care. This method of reimbursement holds physicians accountable for the costs of care incurred throughout maternity care by offering financial incentives to keep risk-adjusted spending low. Using a difference-in-differences approach, I find no evidence of overall changes in spending or the likelihood of Cesarean section for maternity episodes in Tennessee relative to episodes in comparable states. There is some evidence, however, that physicians reduced emergency department visits and the likelihood of postpartum inpatient care. Physicians responsible for the delivery also responded by increasing documentation of less clinically-relevant comorbidities. I find a limited impact on health outcomes. In the second chapter (with Abby Alpert and Mireille Jacobson), we explore the effects of a prescription drug monitoring program (PDMP) mandate in Kentucky, disentangling supply and demand side channels and the role of information versus hassle costs. While PDMPs are designed to provide physicians with information to improve opioid prescribing, mandates also introduce a hassle cost to writing opioid prescriptions. Focusing on the emergency department setting and using Optum Clinformatics claims data, we show that relative to states without a mandate, opioid prescriptions declined sharply in Kentucky for both opioid naive and non-naive patients after the mandate, implying an important role for hassle costs. Among patients presenting with conditions that are clinically appropriate for opioids, there was no decline among opioid naive patients, but prescribing declined for non-naive appropriate patients, suggesting that doctors also use the information in the PDMP. On net, although the PDMP mandate clearly affected prescribing through the information provided, we show that the additional hassle costs from the mandate explain the majority of the decline in prescribing.