Unscreened blood transfusions continue to be one of the major modes of transmission of the human immunodeficiency virus (HIV) in developing countries, such as in Central Africa, where 5% to 18% of blood donors are HIV seropositive. We evaluated a rapid latex agglutination assay using a novel recombinant envelope polypeptide of HIV for the detection of HIV antibodies among 2820 blood donors and clinical patients from diverse geographic regions, including on-site testing in Central Africa of 1600 blood donors. Overall, 29.2% of the serum samples were positive by Western blot assay. On a single determination, the latex agglutination slide test was found to be highly sensitive and specific compared with Western blot results in these populations with a relatively high prevalence of infection. Use of this assay will allow the immediate implementation of serologic screening for HIV in developing areas of the world, where standard screening procedures are impractical or not available, and in many other clinical settings, such as sexually transmitted diseases clinics and hospitals, where testing and counseling could be promptly implemented.