This study will evaluate patients with complaints of dry mouth to determine the cause and severity of their salivary gland dysfunction and their possible eligibility for other NIDCR protocols. Salivary gland secretions have antibacterial, lubricatory, remineralizing, digestive, buffering and cleansing properties. Impaired function of these glands can cause an increase in tooth decay; a variety of oral hard and soft tissue changes, with painful, burning, or ulcerated oral mucosal; problems chewing, swallowing, and speaking; and diminished taste and smell.