For determining treatment options of tonsillar diseases, the authors compared immunohistochemical differences for IgA immunocytes and measured the changes in concentrations of the serum immunoglobulin A and salivary secretory immunoglobulin A before and after tonsillectomy according to age in 126 cases (60 control cases, 66 tonsillectomy cases). The serum IgA and salivary SIgA concentrations of the control group reached to adult's level at the age of 11 to 13. In the tonsillectomies, the serum IgA concentrations below the age of 10 were higher than that of controls and were decreased to the levels of the controls after tonsillectomy in all ages and the salivary SIgA concentrations were decreased to the levels of the controls at the 30th postoperative day, especially at the age of 5 to 7 and 8 to 10. Morphometric features of tonsils in the group below the age of 8 were more active than those in the group above the age of 8 in the controls. In the tonsillectomies, morphometric features of the tonsils were similar to those in the group above the age of 8, but the reticular part of the crypt epithelium remained significantly. Total number of IgA immunocytes was the highest at the age of 5 to 7 with a decline by age, especially at the age of 19 in the controls. In the tonsillectomy group, the number of IgA immunocytes of the extrafollicular area and the reticular part of crypt epithelium decreased below the levels of the control group. In conclusion, tonsils in preschool children are important as a local immunologic defense mechanism, but no significant changes in the immunologic system occurs after tonsillectomy.