An immunohistochemical investigation was conducted on infiltrating lymphocytes in submandibular glands removed from three cases with unspecific chronic sclerosing sialadenitis of the submandibular gland (unspecific CSSS) which has been described for the first time by Küttner. A high degree of lymphocyte infiltration was recognized and formation of lymphatic follicles was observed. In particular, activated B cells were predominantly observed in that part of the lymphatic follicles which was equivalent to germinal centers. In the T cell subset, the helper/inducer T cells displayed significant dominance over suppressor/cytotoxic T cells, and were distributed in the dark peripheral zone of the follicles. The distribution pattern of these lymphocytes seemed to be similar to antigenically stimulated lymph nodes and it was recognized that the unspecific CSSS could be a site of exceedingly active local immune responses. The authors believe that these findings support the view that unspecific CSSS (Küttner tumor) is an immune disorder.