The palatine tonsils which are located in the entrance of digestive and upper respiratory tracts are the most important organs in anatomical and functional structures of the pharyngeal lymphatic tissues. As for function of the tonsil, there have been many suspected theories that included hematopoietic, hormonal, digestive function and production of vitamin, entry of bacteria with other antigenous materials and defence mechanism of which was taken charge by virchow in 1860 in the past. But among these theories, recently, defence mechanism of the tonsil was strongly accepted immunologically. For the purpose of elucidating immune response of the tonsil, the author observed serum immunoglobulin levels, peripheral total lymphocyte counts and populations of T, B and Null lymphocytes before and after tonsillectomy in 30 cases of patients with chronic tonsillitis and 29 cases of healthy controls. The results obtained were as follows ; 1) Serum IgM level was significantly higher in patient group than in control group but was not significantly different preoperative from postoperative patient group. 2) Population of T-lymphocyte more significantly decreased in patient group than in control group but it was not significantly different preoperative from postoperative patient group. 3) Population of B-lymphocyte more significantly increased in patient group than in control group but it was not significantly different preoperative from postoperative patient group. On the basis of these results, it may be suggested that tonsil plays a role in the immune response of human.