HIV/AIDS research and interventions have targeted high risk, male-to-female transgender individuals (MTFs), but their male partners have been largely overlooked. Because of the high rates of HIV infected MTFs, the male partners of MTFs (MSMTFs) are also at high risk of HIV infection. However, the location that MSMTFs occupy in the epidemiology of HIV/AIDS remains unknown. In addition to HIV risk, MSMTFs encounter the negative mental health effects of stigma resulting from their affiliation with MTFs--an already marginalized population--which in turn creates yet another barrier to HIV prevention efforts. MSMTFs remain absent from studies of men's health and, as a result, there are no recognized labels or language available to describe their identities and behavior. The overall goal of this study is to establish a foundation for ongoing research on MSMTFs that will foster their inclusion in HIV/AIDS and public health research agendas. This is an ethnographic study that will describe the behaviors of a sample of MSMTFs, describe the ways MSMTFs construct personal identities, and explore the social geography of HIV risk. This exploration of behaviors, identities and social spaces has the potential to capture the complexities of these types of practices, situate them in a wider cultural construction of masculinity, and inform public health strategies to prevent HIV infection and transmission at individual and institutional levels.