Virologic and seroimmunologic parameters were determined in 56 persons infected with human immunodeficiency virus (HIV). The provirus level varied from 10 to 100,000/10(6) CD4+ lymphocytes, and genomic HIV RNA was detectable in 39 of 56 patients at a relative concentration varying from 10 to greater than 250 copies/mL of serum. Provirus expressed as copies per 10(6) CD4+ lymphocytes and as circulating virus per milliliter of serum increased with disease progression and decrease of CD4+ cell concentration. The mean provirus concentration expressed per milliliter of blood varied little among categories of patients with various levels of CD4+ cells, but there was a progressive increase of circulating HIV genomic RNA. These virologic data suggest that during the course of HIV infection, an increasing proportion of the remaining CD4+ lymphocytes harbor the HIV genome and produce infectious virus. Finally, there was a marked correlation between increased provirus and genomic RNA concentration and three seroimmunologic markers: decrease in CD4+ cell count, p24 antigenemia, and disappearance of antibodies to HIV core antigen.