Lymphocyte subset analysis was performed on 114 healthy children and 84 healthy adults. Samples were prepared by a whole blood lysis technique and analyzed by flow cytometry. The percentage and total number of CD3+, CD4+, CD8+, and CD19+ lymphocytes were calculated for each of six age groups. A direct correlation with age was seen in the percentages of CD3+, CD4+, and CD8+ lymphocytes. The absolute number and percentage of total lymphocytes, the percentage and absolute number of CD19+ lymphocytes, and the absolute number of CD3+ lymphocytes decreased with age. No significant correlation with age was observed for white blood cells, the absolute number of CD4+ and CD8+ lymphocytes, and the CD4+/CD8+ ratio.