With the FACSCount flow cytometer, counts of CD4, CD8 and CD3 lymphocytes and CD4/CD8 ratios were performed in a rural hospital in Tanzania. A total of 168 subjects (21 HIV-1 seropositive and 147 HIV-1 seronegative) were tested as part of a population-based serosurvey and AIDS education programme; 134 other subjects were hospitalized patients who had signs and symptoms suggestive of AIDS (69 HIV-1 seropositive and 65 HIV-seronegative). Mean values for the 147 HIV-1 seronegative subjects from the local population were 980 CD4 cells (95% CI 930, 1031), 598 CD8 cells (560, 635) and CD4/CD8 ratio 1.78 (1.68, 1.89). Seropositive subjects from the local population had significantly lower CD4 cell counts, higher CD8 counts and a lower CD4/CD8 ratio. CD4 cells were significantly lower and CD8 cells significantly higher in HIV-1 seropositive hospital patients compared to HIV-1 seronegative patients. However, 23 (35%) seronegative hospital patients had CD4 counts lower than 600. These results establish baseline values for the lymphocyte subsets in this population and indicate that this technique can be used in remote areas to monitor progress of HIV-infected individuals.