PROJECT SUMMARY This renewal application requests funding for the Brown School’s Training Program in Mental Health Services Research at Washington University in St. Louis (Wash U). Our program will prepare 2 pre- and 2 post-doctoral trainees per year to acquire advanced mental health services research skills to address challenges faced by the most vulnerable populations in our nation. Specifically, persons living with mental disorders who seek care at the intersection of multiple services sectors, experience high needs for care, and are the least likely to secure needed services or to obtain high quality care. Our training program includes five knowledge domains: mental health services research, research with vulnerable populations, intervention research, implementation science, and advanced research methods (e.g., systems science, mixed methods). A team of 30 highly talented mentors led by Dr. Leopoldo J. Cabassa, Associate Professor at the Brown School, supports our training program. Our faculty are drawn from 4 Schools and 6 Departments across Wash U. They have a distinguished record of accomplishment in mentoring and active NIH-funded research in the critical knowledge domains of our program. An exceptional transdisciplinary training environment including 17 research centers at the Brown School, the Institute of Public Health, and the Institute for Clinical and Translational Science supports our program. Building on our 25-year history of successfully training mental health services researchers, our program continues to innovate with the following enhancements. We strengthened our methodological training by adding new courses and faculty mentors conducting cutting-edge research in systems science, health disparities research, implementation science, and advanced data analytics. We added a Steering Committee (SC) composed of leaders in health and mental health services research from inside and outside Wash U and new training opportunities for our faculty to enhance their mentoring skills. We enhanced trainees’ scientific networking by requiring a learning site visit to existing NIMH-funded mental health services studies across the U.S. We added workshops to improve trainees’ science communication skills to better disseminate their work to a broader audience. The overall mission of our program is for our trainees to acquire mental health services research knowledge and skills to meet the most pressing needs in the field of social work and to advance the public health significance and impact of NIMH-services research.