In the labial salivary glands (LSGs) of 16 primary and 18 secondary Sjögren's syndrome (SS) patients, infiltrating lymphocytes were histologically and immunohistochemically examined; also, the serum levels of rheumatoid factor, antinuclear antibodies, anti-DNA antibodies, anti-SS-A and anti-SS-B antibodies, and immunoglobulins (including IgG, IgM and IgA) were all assayed. An immunohistochemical analysis of the lymphocyte subsets in LSGs revealed that severe lymphocytic infiltration was frequently accompanied by marked B cell accumulation both in primary and secondary SS patients. Furthermore, local B cell accumulation was also closely associated with elevated levels of anti-SS-A and anti-SS-B antibodies and IgG, and this association was statistically significant in the group with primary SS but not in the group with secondary SS. Thus, local lymphocytic infiltration, especially B cell accumulation, in the salivary glands is suggested to be involved in serological abnormalities in primary SS, while complicated autoimmune diseases other than SS may also be involved in serological abnormalities in secondary SS.