Although the link between human mobility and infectious disease spread is well established (Wilson, 1995), scholarly interest in the possible correlation between tourism and HIV/AIDS dissemination is fairly recent (Apostolopoulos &Sönmez, 2001a, 2001b, 2002; Apostolopoulos, Sönmez, &Yu 2002; Clift &Grabowski, 1997; Mulhall, 1996; Sönmez, Apostolopoulos, Yu, Yang, Matilla, &Yu, 2006; Wright, 2003). Sexual interactions that carry STI/HIV risks occur between travellers and locals or other travellers; however, "sex tourism" in particular is an important vector for STI/HIV transmission and has potentially explosive ramifications for public health (Wright, 2003). Sex tourism is specifically motivated by persons interested in finding sexual adventure at destinations where the social norms and restrictions of their home environments are suspended. By virtue of their behavioral interactions with sex workers (a "core group" of efficient transmitters of STIs/HIV) and sex partners back in their home environments, sex tourists have a high risk of both acquiring and transmitting STIs/HIV. Consequently, sex tourists themselves become an STI/HIV core group, along with sex workers, seafarers, and truckers-a concept based on the observation that an infection is endemic among a small sub-population of highly sexually active individuals, from whom it spreads in mini-epidemics to the population at large (Mulhall, 1996). The combination of sex tourists' financial resources, the inherently risky nature of their behaviors, and acute poverty at sex tourism destinations is alarming-particularly when viewed in light of the increasing globalization of both sectors of tourism and sex. This chapter will examine sex tourism in terms of social and economic factors that fuel the activity, discuss types of locations around the world where sex tourism flourishes, and provide case studies of sex tourism destinations where STIs/HIV have become problematic.