Recent advances in full blood count and CD4 technology, coupled with the changing population demographics of the Gauteng region, have necessitated reevaluation of the reference ranges currently in use.A cross-sectional study of 631 female and 88 male HIV-negative participants from the Gauteng region was performed. Full blood count, automated differential and CD4 count analyses were done using the latest internationally accepted technology. Reference ranges were compiled from the 2.5th and 97.5th percentiles for both male and female participant groups, and gender and ethnic comparisons calculated by non-parametric tests.Results of 41 females were removed from the statistical analysis because their results were suggestive of possible anaemia. Full blood count reference interval comparison confirmed gender-specific differences in red blood cell and platelet parameters. Ethnic-specific differences were found for some red blood cell parameters in the black female cohort. In addition, black males and females both generally had lower neutrophil and higher lymphocyte counts than a combined Asian/Caucasian/coloured ethnic group.Comparison of the currently calculated reference ranges with published data and reference values in use indicated that a separate ethnic-specific reference range should be introduced for the percentage/absolute neutrophil count and percentage lymphocytes. In addition, locally derived reference ranges for red cell distribution width (RDW) and CD4 percentage of lymphocytes should be implemented for routine diagnostic testing.