In this work, the serum immunoglobulin (IgG, IgA, IgM and IgD) levels were determined in ten patients with chronic tonsillitis. The serum immunoglobulins were estimated before and two months after tonsillectomy, using the radial immuno-diffusion method. Ten normal individuals with intact tonsils were chosen as a control group. The patients had elevated serum levels of IgG and IgA. These high levels may be due to repeated antigenic stimulation. The IgM and IgD were not significantly higher than in the normal controls. The serum IgG level did decrease significantly following tonsillectomy; the other three immunoglobulins were reduced, but insignificantly. The fall in immunoglobulins may be due to a reduction in the antigenic load, to the removal of immunoglobulin-producing tissue, or to alteration in the oropharyngeal pathogenic bacteria. Tonsillectomy does not seem to compromise immunological integrity or the immunoglobulin-producting apparatus. Estimations of the serum immunoglobulin, or simply of IgA, may help us to select those candidates for adeno-tonsillectomy who will have a good prognosis, or at least to exclude those with an underlying sub-clinical immunodeficiency disease.