To assess a hypothesized trend that persons recently infected with the human immunodeficiency virus (HIV) may have more rapid declines in absolute CD4 T-lymphocyte (CD4+ cell) counts than those who were HIV-infected in earlier years, sequential CD4+ cell counts in three groups who had definable dates of HIV seroconversion between 1978 and 1992 were reviewed. The CD4+ cell counts examined were from some of the longest extant studies in the United States: 100 homosexual and bisexual men engaged in ongoing observational cohort studies in San Francisco, Denver, and Chicago since 1978 (Group 1); 89 persons in South Carolina infected after 1986 (Group 2); and 155 injecting drug users participating in an observational cohort study in Baltimore since 1988 (Group 3). For all groups, individually and in the aggregate, mean CD4+ cell counts declined rapidly in the first year after HIV infection and then stabilized. However, there was no clear trend for lower (or higher) CD4+ cell counts by fixed time after HIV seroconversion among those seroconverting in recent compared with earlier calendar years. These data do not support a hypothesized trend for more rapid loss of CD4 T lymphocytes--and, by implication, more pathogenic strains of HIV-1--among persons acquiring HIV infection in recent years.