Thailand is in the midst of a social and sexual transition that is affecting gender roles, sexual behavior, and, hence, risk for HIV. The continuation of past traditions, such as men having sex with commercial sex workers, coupled with an increasing acceptance of noncommercial premarital sex among young people, is fueling the AIDS epidemic. To examine young people's potential risk for HIV, the author investigated their perspectives on sexual behavior and sexual networking, the continued acceptance of premarital sex with commercial sex workers, and perception of risk for HIV in Chiang Mai. This study suggests that a changing social environment and the response to the AIDS epidemic have resulted in new patterns of sexual behavior that might trigger the dissemination of HIV into a broader network.