Background: Nearly half of Veterans who screen positive for PTSD in VA primary care clinics do not receive VA mental health treatment. To increase timely access to VA care, we must understand Veterans’ access pathways (the series of options offered to, and choices made by, Veterans after a positive PTSD screen that may lead them to VA care). Mapping these pathways is key to understanding who is being lost to VA care and where they are being lost. Further, by examining contextual and individual factors that predict who and where Veterans are falling off these pathways, we will be able to ascertain why these Veterans are being lost. Significance: The proposed IIR is responsive to the HSR&D priorities of both mental health and access to care and will provide insight into the impact of the MISSION Act on mental health access. At the completion of this project, we will provide three distinct deliverables: 1) guidance on where and to whom access interventions should be targeted; 2) policy and practice guidance to aid providers in linking Veterans who screen positive to effective VA care; and 3) a method for classifying Veterans from screening to VA mental health care, which could be extended to other conditions (e.g. suicidality). Innovation and Impact: Past research designed to provide information to improve access to PTSD care has been limited by focusing on the end goal (whether these Veterans do or do not access care) rather than the process by which Veterans arrive at this goal (the access pathways). The proposed project is not only one of the first to consider access to care as a process rather than an end point, it is the only study to propose examining the process of access comprehensively using a method that will generalize to the VA system as a whole, and will be applicable to other healthcare conditions identified by VA-based screening. Specific Aims: The proposed mixed methods study has the following aims: 1. Aim 1: Identify contextual- and individual-level variables that differentiate Veterans classified into a VA initial access step (an immediate response to a positive PTSD screen in primary care likely to lead to VA care; e.g., referral to PC-MHI) from those who were not, including those referred to community care via the MISSION Act. 2. Aim 2: Understand VA providers’ and patients’ experiences with, and perspectives on, why Veterans are lost to VA follow-up care immediately after screening positive for PTSD, including the role of the MISSION Act. 3. Aim 3: Map the access pathway steps hypothesized to follow each of the six initial VA access steps, as well as the step hypothesized to lead to community care provided via the MISSION Act, by leveraging the methods developed in our pilot work. Methodology: Aim 1 will include all Veterans with new PTSD screens in primary care between FY 2017-2019. Data from the VA Corporate Data Warehouse (CDW) will be used to determine Veteran access step classification and to identify contextual and i...