To characterize HIV and AIDS cases in foreign-born persons in King County, Washington, HIV surveillance data were analyzed by place of birth, race and ethnicity, mode of transmission, and year of HIV diagnosis. The proportion of new HIV diagnoses among foreign-born Blacks increased from 3.5% during the 3-year period from 1995 to 1997 to 7.5% during the 3-year period from 2001 to 2003 while remaining stable at 11-12% among native-born Blacks. Rates of HIV diagnoses are 2.8 times higher among foreign-born Blacks (1.7%) than among native-born Blacks (0.6%). Heterosexual transmission accounts for at least 52% of prevalent cases among foreign-born Blacks but only 12% of native-born Blacks. These findings have implications for HIV prevention planning in King County. States and local areas should consider reviewing their own surveillance data to determine the possible impact of foreign-born persons on HIV diagnosis rates.