Project background/rationale: Veterans using Department of Veterans Affairs (VA) healthcare facilities tend to have more chronic diseases than the general population, which frequently require chronic pharmacologic treatment. Appropriate medication management is important to prevent untoward health effects for these Veterans. VA's current policies may result in copayments that are higher in VA for certain medications than in non-VA retail pharmacies, which could encourage use of non-VA pharmacies. Having medication records across more than one healthcare system increases the risk that records will be incomplete, which can lead to unintended adverse reactions. Additionally, medication copayments may be associated with reduced medication adherence. Consequently, VA will change to a 3-tiered system in February 2017 ($5, $8, and $11 per 30-day supply for Tier 1, 2 and 3 medications, respectively), and there will be a cap on annual medication copayments that Veterans have to pay of $700. The VA anticipates that for most Veterans, these new copayment amounts will result in lower out-of- pocket costs, which will encourage greater adherence to prescribed medications and will reduce the risk of fragmented care that results when Veterans use multiple pharmacies. Understanding the impact of the copayment change will be crucial for policymaking and planning. Project objectives: The aims of this study are to 1) determine the impact of the copayment change on patient use of VA pharmacies; 2) examine the impact of the copayment change on patient medication adherence, medication costs, and clinical outcomes; 3) assess the impact of the copayment change on patient-reported medication management experiences; and 4) assess the impact of the copayment change on provider-reported prescribing practices and experiences. Project methods: We will use a mixed methods approach that takes maximum advantage of available data from VA to examine whether the copayment change impacted receipt of medications from VA pharmacies (Aim 1), medication adherence (Aim 2), and Veteran and provider experiences and decision making (Aims 3 and 4). Because the implications of the copayment restructuring will depend on Veterans' decision making (e.g., where to obtain medications) and on providers' prescribing practices (e.g., whether they switch patients to Tier 1 medications), we will conduct surveys and semi-structured interviews to examine patient and provider experiences with the copayment change and its implementation.