In this special issue of AIDS and Behavior, we focus on the social contexts of sexual transmission of HIV/STI in one South China city. Our multiple projects grew from partnerships across the social and biomedical sciences, and with public health experts in Liuzhou City, to address critical gaps in knowledge about how social factors drive heterosexual transmission. The eleven articles that comprise this special issue feature multidisciplinary and mixed method approaches, collecting data in Liuzhou from different populations, environments, and social venues where individuals often find sexual partners. They document heterosexual behaviors and their meanings. They investigate the experiences and behaviors of women and men in social venues, exploring the networks of people within these venues, how they relate to one another, share information, and influence each other. The articles also examine the experiences of people living with HIV, again collecting data from multiple levels and sources, and revealing the ongoing power of stigma to shape these lives. Taken together, the articles demonstrate the critical role of social contexts in shaping behaviors and meanings, which are linked to heterosexual transmission of HIV/STI, and which must be taken into account for the development of appropriate and effective public health interventions.