We examined beliefs about the origin of HIV as a genocidal conspiracy in men and women of four racial/ethnic groups in a street intercept sample in Houston, Texas. Groups sampled were African American, Latino, non-Hispanic white, and Asian. Highest levels of conspiracy theories were found in women, and in African American and Latino populations (over a quarter of African Americans and over a fifth of Latinos) with slightly lower rates in whites (a fifth) and Asians (less than one in ten). Reductions in condom use associated with such beliefs were however only apparent in African American men. Conspiracy beliefs were an independent predictor of reported condom use along with race/ethnicity, gender, education, and age group. Data suggest that genocidal conspiracy beliefs are relatively widespread in several racial/ethnic groups and that an understanding of the sources of these beliefs is important to determine their possible impact on HIV prevention and treatment behaviors.