His work focuses on community-based research efforts targeting racial/ethnic and underserved populations (including immigrants, refugees, and linguistic and sexual minorities) with a history of or who are currently using alcohol, tobacco, and other drugs (ATOD) and engaging in HIV-related risk practices. His NIH-funded research focuses on the social epidemiology of ATOD and HIV/STI (sexually transmitted infection) targeting Asian Americans and Pacific Islanders in the U.S.; and lesbian, gay, bisexual, and transgender individuals in the U.S. and South Africa, as well as China. He is one of the first investigators to examine ATOD use/abuse and HIV-related risks among Chinese money boys (men who engage in commercial or transactional sex with other men) in Shanghai.