For the function of tonsil, there have been various suspected theories, that were included protective, hematopoietic, endocrinologic, vitamin production and digestive function. Since Virchow had been reported that tonsil is protective organ in 1860, the theory of protective funtion was strongly accepted in recently. Tonsil is immunologically lymphoid organ carrying out the function of humoral and cellular immunity, and they form a local protective barrier and may contribute the normal immunological process and they synthesize all classes of immunoglobulin. Author observed serum immunoglobulin A, M, D and G level before and after for 40 cases of adenotonsillectomy and for 24 cases of tonsillectomy and then compared with 10 cases of healthy individual as a control group in Department of Otolaryngology of Hang-Yang University Hospital from September to December 1981. Pre-operative and post-operative serum immunoglobulin levels were measured with Radial Immuno-diffusion Method, and clinicostatistical analysis for achieved datas was performed with IBM Computer at Computer Center of Korea University. The results were followed ; 1) In the adenotonsillectomy group, pre-operative serum immunoglobulin A was 181.15±87.69mg/dl, IgM was 166.42±76.73mg/dl, IgD was 6.27±5.32mg/dl, IgG was 1420.42±298.95mg/dl and post-operative serum IgA was 142.82±54.17mg/dl, IgM was 126.20±57.53mg/dl, IgD was 3.32±3.22mg/dl, IgG was 1219.37±267.23mg/dl. In the tonsillectomy group, pre-operative serum immunoglobulin A was 250.08±92.76mg/dl, IgM was 163.25±53.67 mg/dl, IgD was 4.61±4.35mg/dl, IgG was 1521.87±262.91mg/dl and post-operative serum IgA was 220.25±88.28mg/dl, IgM was 156.04±55.95mg/dl, IgD was 2.79±4.08mg/dl, IgG was 1374.04±255.33mg/dl. In the control group, serum IgA was 116.20±22.31mg/dl, IgM was 115.50±50.18mg/dl, IgD was 3.74±1.31mg/dl, IgG was 1174.20±199.98mg/dl. 2) Pre-operative serum immunoglobulin levels especially IgA and G in chronic tonsillitis patients showed higher than in control group. 3) Post-operative serum immunoglobulin A,M,D and G levels were decreased but similar to the level of control group. 4) There was no significant difference between adenotonsillectomy group and tonsillectomy group.