Tonsil is a kind of mucosal associated lymphoid tissues, and has been known as functioning immune organ. However, immunological roles of tonsil are not yet clear. Systemic immune function could be affected by environmental factors such as age, allergy, infection, and so on. Therefore we try to evaluate the effect of environmental factors on tonsillar lymphocyte subpopulation. After surgical specimens of fresh tonsil were minced mechanically, lymphocytes were separated using Ficoll-Hypapaque and cryopreserved until flow cytometric analysis. Flow cytometric analysis was performed using 11 monoclonal antibodies(CD4, CD8, CD19, CD23, CD25, CD38, Anti-IgA, Anti-IgM, Anti-IgD, Anti-IgE, Anti-HLA-DR). All data were analysed by use of three variavles : age, allergic skin reaction, and frequency of infection. The results were as follows ; 1) Age is regarded as the most important factor affecting on the tonsillar lymphocyte subpopulation. 2) Mature B-lymphocytes expressing surface immunoglobulin-sIgM+D+ and cd23+lymphocytes are increased in adult group, whereas immature sIgM+D- lymphocytes and cd38+sIgD- lymphocytes(plasma cell) are increased in child group. These results suggest that tonsil might actively produce antibody in child. 3) Age, allergic skin reaction, and frequency of infection do not affect on the expression of HLA-DR and IL2 receptor. We hope that our results be used as basic data for the study of immunologic role of tonsil.