Male sex workers are at high risk of HIV infection, and yet, information on their characteristics and risk behaviors are notfully explored in different provinces of Vietnam. This paper aims to describe and compare some characteristic and risk behaviors of male sex workers in three urban cities of Vietnam. Despite the similarities in their high risks of HIV infection, there are differences in various factorsthat are associated with HIV risks. While high mobility in Hanoi might increase HIV transmission risk of partidpants, male sex workers in Ho Chi Minh City have a high prevalence of drug use. High prevalence anal sex with male clients as well as alcohol and drug use before and during sexual intercourse are predominant among partidpants in Nha Trang. HIV prevention programs among MSM should pay attention to diversities in terms of socio-economic characteristics as well as risk behaviors of MSM in different localities.