Background: Posttraumatic stress disorder (PTSD) is one of the most common mental health diagnoses among Veterans. Cognitive processing therapy (CPT) and prolonged exposure therapy (PE) were widely disseminated in the Veterans Health Administration (VHA) as recommended PTSD treatments. Despite these efforts, few post-9/11 Veterans diagnosed with PTSD initiate CPT or PE. In the small percentage of Veterans who receive these therapies, CPT and PE are rarely the first treatment a Veteran receives. A common treatment sequence identified in implementation research, begins with “stabilization treatment,” combinations of psychosocial and medication treatments that prepare Veterans for CPT or PE. A gap in existing research is how treatment sequences, particularly stabilization treatment, influence initiation of CPT or PE. Significance/Impact: PTSD is an HSR&D priority condition due to its substantial negative biopsychosocial impact on Veterans lives. Novel strategies are needed to increase engagement, retention, and improve outcomes from recommended PTSD treatments, and to reduce disparities in access to this care. Understanding how to most effectively combine and sequence PTSD treatment is an HSR&D identified area of interest, and a research gap identified in the VHA PTSD clinical practice guideline. Innovation: Despite consistently identifying stabilization treatment as a common VHA practice, little research has investigated this treatment sequence. A novel approach to solving existing limitations in PTSD treatment delivery involves developing an intervention that both acknowledges the ubiquitous presence and benefits of stabilization treatment, while facilitating timely transition from stabilization treatment to CPT or PE. Specific Aims: This CDA-2 aims to improve delivery of PTSD services in the VHA, while simultaneously providing me with training in health services research methods to support my development into an independent VHA researcher. The proposed research aims are: (1) To qualitatively understand Veterans’ and clinicians’ perspectives on selecting stabilization treatments and how stabilization treatment serves as a barrier or facilitator of transition to CPT or PE; (2) To develop and conduct a randomized, pragmatic pilot trial of a brief, Veteran-centered intervention to support transition from stabilization treatment to CPT or PE; and (3) To identify sociodemographic disparities in treatment sequences and to determine how treatment sequences influence time to CPT or PE initiation across the VHA. Methodology: I will then conduct qualitative interviews with a national sample of Veterans (n=30) and clinicians (n=20; Aim 1). Using rapid qualitative analysis procedures, I will evaluate how treatment sequences, particularly stabilization treatment, are chosen and how they serve as a barrier or facilitator of transition to CPT and PE. I will then use knowledge gained from Aim 1 to develop a health services intervention that facilitates timely tra...