Clinical and pathological evidence suggests that a wide spectrum of lymphoproliferation exists in Sjögren's syndrome (SS), from benign disease with lymphoid infiltrates confined to glandular tissue on the one end, to widespread lymphoreticular malignancy on the other. In the middle of the spectrum are patients threatened by extraglandular extension of lymphoproliferation which is not clinically or histologically malignant and which apparently has the potential to regress with appropriate therapy or to progress to frank neoplasia. Illustrative patients are described. Over thirty other case reports associating SS with pseudolymphoma, Waldenstrom's macroglobulinaemia, reticulum cell sarcoma, or other lymphomas appear in the literature. Similar lymphoproliferative processes have been observed in other autoimmune diseases, in certain immune deficiency states, with hydantoin and other anticonvulsant drugs, and in experimental animal models. In SS, as in these other conditions, it seems likely that a combination of genetic, immunologic, and viral or other unknown environmental factors plays a role in pathogenesis.