An immuno-histological study for the intracelluar immunoglobulin production in human palatine tonsils has been performed by unconjugated peroxidase-antiperox-idase (PAP) staining method. The rabbit antiserum to human immunoglobulins (IgG, IgA, IgM) was linked to the PAP complex by an intermediate stage of swine antiserum to rabbit immunoglobulin. Immunoperoxidase methods permit the specific demonstration of cells and tissue antigen in a variety of fixed tissues. The unique concept in the peroxidase-anti-peroxidase (PAP) technique is the use of unconjugated antibodies in the PAP reagent. This may well be the reason for the extremely high sensitivity of the method, which is permitting reliable and consistent demonstration of antigens in the fixed paraffin-embeded tissues. The routine formalin-fixed, paraffin embeded sections were stained with HE for histologic evaluation and the DAKO PAP kit was used for immunoglobulin demonstration. All the lymphoid follicles of the palatine tonsils had germinal centers and were divided into three zones ; two forming the follicle center (zone a, b) and the third (zone c) forming the lymphoid cap. Immunoglobulin synthesis appeared from the zone b at the beginning and migrated to the zone c and other perifollicular area. In this study, the majority of specimens showed reactive hyperplasia where the immunoglobulin containing cells were located mainly in the zone b, subepithelial area including zone c. The follicular centers were entirely composed of cells negative for immunoglobulin. IgG and IgA were dominant immunoglobulins and small number of IgM containing cells were also present. These results suggested that the antigen could contact directly with crypt epithelium, and lead lymphocytes to permeate into the epithelial layer and zone c. The immunoglobulin producing cells could migrate to the perifollicular and subepithelial layer and the sensitized lymphocytes remained in the epithelial and just beneath the epithelial layer of crypt where it could react with subsequent antigenic challenge.