ABSTRACT The annual “Principles of STI and HIV Research and Public Health Practice” course was launched by the University of Washington in 1993 to provide an intensive overview of skills and foundational knowledge needed to pursue a research career in the field of STI/HIV. Since then, ~3,150 trainees have attended this annual course. The proposed R13 is for partial support of the 2021 course, as a training conference. Course objectives are to: (1) Describe the biologic, clinical, epidemiological and social/behavioral aspects of STI of contemporary public health importance; (2) Identify outstanding scientific questions and develop a research design or program evaluation to answer these scientific questions; (3) Gain experience applying different strategies from research and/or public health program evaluation to answer emerging questions in the field of HIV/STI; (4) Gain experience working on a multidisciplinary teams of STI/HIV researchers and practitioners and provide opportunities for social interaction and networking; (5) Discuss the different opportunities and career paths available in STI/HIV research and practice fields for US domestic and international public health; and (6) Provide opportunities for professional networking with peers and course faculty To meet these objectives, the course takes an interdisciplinary approach and provides early stage investigators with tools for continued learning, collaboration in multidisciplinary teams, and maintaining a broad scope of investigative possibilities. This course offers a unique opportunity for state-of-the-art introductory training in behavioral, clinical, epidemiologic, statistical, implementation, and basic science research on STI/HIV through a practically-oriented overview of concepts and skills common to these broad disciplines. Course proceedings are disseminated on a UW website, which contains speakers' slides, lecture recordings, and key references. The course is evaluated each year, and updates to subsequent course agendas are informed by participant feedback and discussions among course Curriculum Committee members to ensure the course is up-to-date, relevant, and employs active learning techniques. The 28th annual course in currently underway in 2020 (in a virtual format), and participant feedback remains extremely positive, demonstrating that the “Principles Course” remains a critical resource for training the next generation of HIV/STI researchers and public health practioners.