Objective        To compare the sexual behavior and AIDS-related knowledge among men having sex with men (MSM) with different sex orientation in China’s western region.       Methods        Cross-sectional surveys were conducted to 1 275 self-identified gays and self-identified bisexual men selected by non-randomly sampling in Chongqing City

Sichuan Province and Guangxi Zhuang Autonomous Region during July 2009 to March 2010. The information was collected by face-to-face anonymous questionnaire survey

and analyzed by cochran-mantel -haenszel (CMH) method.       Results        There were 975 gay-identified men and 301 bisexual-identified men enrolled in this study. The proportion of the married was higher in bisexual-identified men than the gays (27.24% vs 13.55%

P0.05). In recent 6 months

there were more temporary male partners in bisexual-identified men than in the gays

but the latter were more likely to use condom for insertive behavior with temporary partners (50.61% vs 43.18%

P0.05). The proportion of whom having female sexual partners were 6.78% and 31.23% respectively (P0.05). In terms of self-efficacy of condom use

knowing the proper way of using accounted for 92.09% and 83.72% respectively for the gays and the bisexual

actively refusing unprotected sex accounted for 60.47% and 51.83% respectively

and successfully persuading their partners to use condom accounted for 70.74% and 62.46% (P0.05). The gay-identified men had higher proportion of free HIV testing than bisexual-identified men (69.20% vs 57.81%

P0.05). There was statistical difference in the proportion of obtaining information about HIV/AIDS via internet and peer education (P0.05).       Conclusion        Compared with gay-identified men

the bisexual-identified men have a higher rate of unprotected sex and less consciousness of risk and self-protection. More efforts should be exerted for behavioral interventions. While

the self-identified gays have relatively more intense perception of AIDS discrimination and stronger stigma effect. Peer education and internet intervention should be actively carried out in order to transform AIDS knowledge into protective behaviors to reduce their HIV infection and transmission.