OBJECTIVE To determine the relative frequencies of HIV-1 p24 antigen and culture positivity in white and black patients. METHODS Volunteers in the US military's HIV natural history study were 46% white, 44% black, 7% Hispanic and 3% other. Focusing on the comparable groups of whites and blacks, a retrospective analysis was performed of the results of virologic assays collected over a 2-year period. METHODS p24 antigen was quantitated in sera with and without immune complex dissociation (ICD); viral isolation was performed by coculture of peripheral blood mononuclear cells. RESULTS Results of the two virologic assays were very similar in the two racial groups, both overall and after stratification by CD4 cell count. As reported previously, the concentration of serum immunoglobulin G was found to be greater in black than white subjects. In contrast to results with ICD, sera tested without ICD resulted in differing (higher) rates of antigenemia in whites than blacks (P = 0.002). CONCLUSIONS The frequencies of p24 antigen and culture positivity were found to be independent of race. Previously observed racial differences in antigen positivity were likely to be due to more extensive antibody binding in blacks than in whites.