Sjögren's syndrome (SS) is a chronic, slowly progressive, inflammatory, autoimmune disease characterized by (1) lymphocytic infiltration of the exocrine glands leading to diminished or absent glandular secretion, and (2) marked B-lymphocytic cell hyperreactivity manifested initially by a variety of serum autoantibodies, including those against the Ro(SSA) and La(SSB) ribonucleoproteins, ending in the development of B cell non-Hodgkin's lymphoma in a substantial number of patients. Most patients with SS present only with keratoconjunctivitis sicca and xerostomia. However, approximately 40% develop extraglandular manifestations that present in two ways: (1) the development of lymphoepithelial lesions in several extra-exocrine gland tissues (i.e., bronchi, renal tubules, or biliary ducts), and (2) vasculitis related to the deposition of immune complexes due to B cell hyperreactivity. Pulmonary manifestations develop in some patients and may present as (1) bronchitis sicca; (2) a wide spectrum of lymphoproliferative diseases, ranging from bronchus-associated lymphoid tissue (BALT) hyperplasia, lymphoid interstitial pneumonia, and B cell non-Hodgkin's lymphoma mainly of the extranodal marginal zone B-cell lymphoma of BALT-type or rarely of higher-grade malignancy; and (3) other interstitial pneumonias. Pleuritis can be seen in SS patients with associated systemic lupus erythematosus or rheumatoid arthritis.