Sjögren's syndrome (SS) is a chronic inflammatory disease of unknown cause characterized by diminished lacrimal and salivary gland secretion resulting in keratoconjunctivitis sicca and xerostomia. There is dryness of the eyes, mouth, nose, trachea, bronchi, vagina, and skin. In half of patients, the disease occurs as a primary pathologic entity (primary Sjögren's syndrome). In the other half, it occurs in association with rheumatoid arthritis or other connective tissue disorders. Ninety percent of patients with Sjögren's syndrome are female. The mean age at onset is 50 years, although the disease does occur in children.