This study investigated the association of age with CD4+ cell counts of HIV patients receiving antiretroviral treatment (ART) over a 4 year period. Data were collected from 126,672 previously treatment-naïve patients in 4 Sub-Saharan African nations. The baseline CD4+ count was measured at onset of ART and at 6-month intervals thereafter. The predictor variable was the age at initiation of therapy with ages grouped in five 10-year ranges: 20-29, 30-39, 40-49, 50-59, and 60 and over. The following 8 baseline covariates were also noted: sex, WHO stage, functional status, active TB infection, active cryptococcal disease, active P. jiroveci pneumonia, other active opportunistic infections, and ART regimen. The resulting dataset includes 466,482 repeated CD4+ count measurements with demographic and other patient-related characteristics.