Thomas W. Valente, PhD, is Professor in the Department of Population and Public Health Sciences, Keck School of Medicine, at the University of Southern California. He has authored two books on social network analysis and one on evaluating health promotion programs. Valente has published widely in the fields of public health, networks, and communication, he has been applying social network theories and methods to public health for over 30 years and has worked on system implementation and transformation. He can be reached at tvalente@usc.edu.