Recently, considerable concern has been raised regarding the possibility that antibody-based screening tests for the human immunodeficiency virus (HIV) may fail to detect certain high-risk individuals for prolonged periods of time. It has been proposed that testing for HIV-related antigen may be a necessary procedure to detect such individuals. To address this issue, we longitudinally studied two groups of homosexual men: direct sexual partners of acquired immunodeficiency syndrome (AIDS) or AIDS-related complex (ARC) patients and individuals who ultimately sero-converted. There was no evidence of prolonged infection with HIV in the absence of detectable antibody in these two groups. It appears at this time that, even among subjects at very high risk for HIV infection, currently available antibody-based assays are sufficient to identify infected individuals.