Stigma may mediate some of the observed disparity in HIV infection rates between black and white men who have sex with men (MSM). We used data from the General Social Survey to describe race-specific trends in the US population's attitude toward homosexuality, reporting of male same-sex sexual behavior, and behaviors that might mediate the relationship between stigma and HIV transmission among MSM. The proportion of blacks who indicated that homosexuality was "always wrong" was 72.3% in 2008, largely unchanged since the 1970s. In contrast, among white respondents, this figure declined from 70.8% in 1973 to 51.6% in 2008 with most change occurring since the early 1990s. Participants who knew a gay person were less likely to have negative attitudes toward homosexuality (relative risk, 0.60; 95% confidence interval, 0.52 to 0.69). Among MSM, twice as many black MSM reported that homosexuality is "always wrong" compared with white MSM (57.1% versus 26.8%, P = 0.003). MSM with unfavorable attitudes toward homosexuality were less likely to report ever testing for HIV compared with MSM with more favorable attitudes (relative risk, 0.50; 95% confidence interval, 0.31 to 0.78). US attitudes toward homosexuality are characterized by persistent racial differences, which may help explain disparities in HIV infection rates between black and white MSM.