This study was undertaken to establish local CD4+LC standards, which could be used as indicators of immune deficiency or monitor progress of HIV therapy, instead of relying on Caucasian standards, which may not exactly reflect Nigerian CD4+LC sub-populations. CD4+LC from 1232 Nigerian adults were studied. They included 852 apparently healthy individuals, 172 HIV-positive persons with no major AIDS defining illnesses (AIDSDIL) and 208 HIV infected individuals with AIDSDIL. The mean CD4+LC of healthy Nigerians (821 +/- 12) was more than two times higher than the mean CD4+LC of HIV-positive individuals without AIDSDIL (369 +/- 14) and almost five times higher than the mean of HIV-positive individuals with AIDSDIL (163 +/- 13) (p < 0.05). In addition, a CD4+LC of < 200 cells/uL can be considered as an AIDS defining laboratory criterion in Nigerians as the 208 individuals with AIDSDIL had a mean CD4+LC of 163 cells/uL. This study therefore establishes a local standard range for CD4+LC in healthy and HIV infected Nigerians which can serve as reliable indices for HIV induced immune impairment and for monitoring effectiveness of HIV therapy.