Patients will return every two years from the baseline visit for a full oral examination, salivary function assessment, clinical laboratory studies, and questionnaires concerning signs and symptoms of salivary gland dysfunction. These individuals will be patients with Sj(SqrRoot)(Delta)gren's syndrome (SS), incomplete SS (patients who have some, but not all of the criteria for SS) or radiation-induced salivary gland hypofunction. We anticipate that many of these patients will also participate in therapeutic trials conducted within the branch.