Previous studies have documented disparities in HIV prevalence by race among men who have sex with men (MSM), even after adjusting for traditional risk factors. In this analysis of data collected for the 1999-2000 Los Angeles Young Men's Survey, a cross-sectional venue-based survey of MSM aged 23-29, we investigated whether information on male sex-partner characteristics accounts for some of the racial/ethnic differences in HIV prevalence. In this sample of survey participants, we observed that African American MSM reported similar or lower levels of HIV risk behaviors compared with White MSM but much higher HIV prevalence (26% vs. 7.4%, respectively). In an unadjusted logistic regression model, African American participants had 4.4 times higher odds of HIV infection compared with White participants. In a multiple logistic regression model adjusting for participant behaviors, we observed elevation of the relative odds of HIV infection for African Americans compared with Whites (odds ratio [OR] = 6.9, 95% confidence limits [CL] = 2.5, 19). In a fully adjusted model, controlling for the effects of having older partners and more African American partners, we observed a 20% reduction in the relative odds of HIV for African American participants compared with White participants (OR = 5.5, 95% CL = 1.8, 17). Our findings suggest that differences in male partner types, namely older and African American partners, may account for some of the observed racial disparity in HIV infection, especially for African American MSM compared with White MSM in Los Angeles.