This paper presents laboratory and clinical data on 27 children of the ages between 6 and 11 yr, who, in connection with tonsillectomy 2 1/2 yr earlier, had low serum and saliva Ig[immunoglobulin]A levels, low serum IgE levels and a considerable lack of IgA and IgE plasma cells in the excised tonsils; correlation between deficiency in IgA and culture of pathogenic bacteria from the tonsils was significant. From clinical point of view, 22 of children had benefit of the tonsillectomy and no longer had a tendency towards a development of recurrent infections. The remaining 5 patients continued to complain of recurring respiratory infections; in addition, levels of serum and saliva IgA were low. Four of these 5 children harbored pathogenic bacteria in their throats. Many of the 27 patients still had low serum IgA and IgE levels as compared with levels in healthy, age-related controls; in 3 patients the IgE levels in serum had risen considerably parallel with the development of atopic diseases. Saliva IgA was rather constant after tonsillectomy as compared with the preoperative levels, though it had risen in some of the children. IgG and IgM had decreased significantly; the question is raised, whether this was due to the tonsillectomy, by the removal of chronically infected organs or by the removal of important immunological tissue.