Data from 307 young migrant men who have sex with men (MSM) in Beijing were analyzed to examine bisexual behavior and the associated sociodemographic and behavioral factors among Chinese young migrant MSM. More than one-fourth (27%) of the MSM were also concurrently engaged in sexual behavior with women (MSMW). Among MSMW, 8.4% were infected with HIV, and 10.8% with Syphilis, compared to 4.9% and 23.7%, respectively, among men who have sex with men only (MSM-only). Various HIV-related risk behaviors among MSMW were similar to those of MSM-only, such as unprotected anal sex, multiple sexual partners, involvement in commercial sex, and substance use. Compared with MSM-only, MSMW were less likely to have tested for HIV, to participate in HIV prevention activities, and were less knowledgeable about condom use and HIV/AIDS. MSMW also had a higher rate of unprotected sex with female stable sexual partners than with male stable sexual partners (79.5% vs. 59.5%). Results indicated that MSMW were at a very high risk for both HIV infection and transmission. Intervention efforts are needed to target this subgroup of MSM and promote AIDS knowledge and HIV/STD testing among MSMW, and to reduce HIV transmission through MSM's bisexual behavior.