Sjögren's syndrome (SS) is a multi-system exocrinopathy. Its aetiology remains unknown and it has an auto-immune pathogenesis. Although SS has been reported in young children and men, it is more frequent in middle-aged women. SS may occur alone, defined as primary SS, or in association with another auto-immune disease, defined as secondary SS. SS has a wide variety of glandular and extra-glandular manifestations affecting almost every organ. Despite its apparently inoffensive initial manifestations, SS can become a disabling and potentially life-threatening disease. This book discusses Sjögren's syndrome in detail, and provides further insight on topics that include the clinical manifestation and management of SS; the symptoms and diagnosis; health related quality of life in patients with SS; the involvement SS has in the central nervous system; and new aspects of mechanism of salivary glands dysfunctions in SS.