Objectives. We estimated the number and cost of syphilis-attributable HIV cases among African Americans. Methods. A mathematical model of HIV transmission was used to estimate the number of partnerships consisting of HIV-discordant African Americans in which infectious syphilis was present and the number of new HIV cases attributable to syphilis in these partnerships. Results. In 2000, an estimated 545 new cases of HIV infection among African Americans could be attributed to the facilitative effects of infectious syphilis, at a cost about $113 million. Conclusions. Syphilis prevention could reduce HIV incidence rates and the disproportionate burden of HIV/AIDS on the African American community, resulting in substantial reductions in future HIV/AIDS medical costs.