Project Summary/Abstract This is a request for a continuation of the Biostatistics and Epidemiology in AIDS Training Program at the Harvard T. H. Chan School of Public Health (HSPH). The program prepares predoctoral and postdoctoral trainees in the application of biostatistics and epidemiology to HIV research, and the development of new methodology relevant to this research. The program is an active collaboration between the HSPH Departments of Biostatistics and Epidemiology. Trainees receive high-quality instruction in core biostatistical theory and methods, such as probability, statistical inference, computing and data analysis. The program also provides training in specialized topics of particular relevance for HIV applications, such as survival analysis, longitudinal and multivariate data analysis, causal inference, and genetics, with options in the increasingly important areas of computational biology/bioinformatics and health data science. The training also includes substantive course work in HIV-related topics, most commonly in HIV epidemiology; topics in immunology, virology and infectious diseases; or HIV-related health policy. Trainees participate in a collaborative HIV-related project with clinical and laboratory science researchers; a regular “HIV Working Group” seminar series where faculty, trainees and other researchers present their HIV-related research; and seminar discussions about the design of developing clinical trials and observational studies in HIV research organized by the HSPH Center for Biostatistics in AIDS Research (CBAR). An important focus of training is the opportunity to work with faculty on HIV-related biostatistical and epidemiological methods research including, for predoctoral students, the development of a doctoral thesis. Trainees participate in formal courses on scientific integrity in the conduct of research and reproducibility of research, and workshops on effective writing, public speaking, and career development. Since its inception in 1988, this training program has emphasized strong links to HIV research, particularly through the large statistical centers at CBAR working with international HIV clinical trials research networks and the Pediatric HIV/AIDS Cohort Study, and through collaborations with the Botswana Harvard Health Partnership and other sub-Saharan HIV-related projects. The Program has a particular focus on supporting a pipeline of applicants from underrepresented minority groups and their success in completion of training. The focus on interdisciplinary training at HSPH, as well as its talented and diverse student body and faculty, makes it well suited for a training program in biostatistics and epidemiology applied to HIV research.