One of the variants of IFA using a conjugate on the basis of anti-HIV-IgG was used for control of the content of human immunodeficiency virus (HIV) antigen at different stages of production of a test system for serodiagnosis of AIDS. This method permits HIV antigen quantitation in virus lysates, its nonpurified concentrates, and in native culture fluid in titres from 2000 to 60,000 and from less than 27 to greater than 729, respectively. In most cases, high titres of antigen in the liquid fraction of the culture corresponded to high values of the antigen-containing cells on the basis of immunofluorescence data and signs of intensive HIV production in electron microscopic culture control. The authors developed a method allowing to determine the antigen titre in the study material using only one dilution (1:9) of it in IFA technique.