Initial CD4 lymphocyte counts were studied in 244 patients with human immunodeficiency virus (HIV) seroconversion. The CD4 cell counts at initial presentation after seroconversion were normally distributed (mean, 579/mm3; SD, 252). The mean percentage of CD4 cells was 26.1% (SD, 5.6). CD4 cell counts were < 500/mm3 in 41% and < 200/mm3 in 4%. The mean calculated duration of HIV infection was 7.7 months, which was not significantly different between the highest and lowest CD4 count quartiles (8.1 vs. 7.9). Age, sex, race, and serologic evidence of toxoplasmosis, cytomegalovirus, hepatitis B, syphilis, and varicella-zoster virus were not associated with initial low CD4 cell counts; however, never-married men were significantly overrepresented in the lowest quartile. These findings suggest that extensive CD4 lymphocyte depletion is common in early HIV infection and that frequent screening is necessary to identify newly infected patients who would benefit from antiretroviral therapy.