Harold D. Green, Jr. (Hank) is a senior behavioral scientist at the RAND Corporation, a professor at the Pardee RAND Graduate School, and the director of the RAND Center for Applied Network Analysis and System Science. Green uses network analyses to understand the social and cultural determinants of health. Green leads a longitudinal study funded by the National Institutes of Health (NIH) that investigates influence and selection processes associated with substance use and other risk behaviors among U.S. adolescents. Other projects focus on HIV-related conspiracy beliefs among HIV-positive African-Americans in Los Angeles; sexual health and risk-taking among men who have sex with men, commercial sex workers, and transgender individuals in Beirut; and how changing network composition and structure are linked to HIV care adherence among HIV-positive Ugandans. Green also investigates connections among network structure, network composition, substance use, and risky sexual behavior among people experiencing homelessness. Green is active in designing and implementing specialized software to collect longitudinal personal network data, developing a new conceptual model for understanding network-based influences on health behaviors, exploring the impact of missing data on statistical models that link network structure to individual behaviors and attitudes, and applying new statistical methodologies for the analysis of personal network data. Green holds a Ph.D. in anthropology from the University of Florida and is an alumnus of the University of Illinois training grant in quantitative psychology; the Center for Supercomputing Applications Center for the Humanities, Arts, and Social Sciences; and the Science of Networks in Communities Research Group.