Theo Sandfort, Ph.D., is HPTN 075 protocol chair and professor of Clinical Sociomedical Sciences (in Psychiatry) at Columbia University and a research scientist at the New York State Psychiatric Institute. He is trained as a social psychologist in the Netherlands, where he was chair of the Gay and Lesbian Studies Department at Utrecht University. In 2001, Theo moved to New York and joined the HIV Center for Clinical and Behavioral Studies.