ABSTRACT In this K23 proposal, Dr. Jonathan Ross describes a mentored research project and a rigorous career development plan that will help to establish him as an independent and productive clinical investigator with expertise in assessing and improving outcomes along the HIV care continuum in international, resource-limited settings. The 2015 World Health Organization guidelines recommend antiretroviral therapy (ART) for all people living with HIV (PLWH) regardless of CD4 count (universal ART). However, despite the tremendous scale-up of ART in sub-Saharan Africa over the past two decades, many PLWH do not initiate ART or remain in care. To ensure the success of treatment expansion to all PLWH, it is critical to understand factors associated with not initiating or remaining on ART under universal treatment and then develop targeted approaches to improve uptake of and retention on ART. The overall goal of this project is thus to identify determinants of ART uptake and retention under universal ART, and design a targeted and informed intervention to minimize loss to care. The proposed study will be conducted in Rwanda, one of the first countries in sub-Saharan Africa to implement universal ART, and will leverage the existing infrastructure of the Central Africa International Epidemiologic Databases to Evaluate AIDS, an established cohort of over 65,000 PLWH. Using mixed methods and the Andersen Behavioral Model of Health Services Utilization as a framework, Dr. Ross will: (1) identify the rates and predictors of ART uptake and retention among patients initiating HIV care under universal ART; (2) identify barriers to and facilitators of ART uptake and retention under universal ART; and (3) develop an intervention to improve ART uptake and retention of patients at high risk of loss to care, and pilot test its feasibility and preliminary efficacy. To accomplish these aims, he will pursue additional training in: (1) statistical analysis of longitudinal and clustered data, (2) advanced qualitative methods, (3) development of health services delivery interventions in resource-limited settings, and (4) conduct of clinical and health services research in international, resource-limited settings. With completion of these activities, along with guidance from a multi-disciplinary team of expert mentors, Dr. Ross will obtain the skills necessary to achieve his career goal of becoming an independent investigator.