The sensation of dry mouth is a common problem, often neglected. The decrease of salivary flow causes chronic oral discomfort and functional problems and predisposes to rampant dental caries and oral candidiasis. Various methods are described to evaluate salivary gland hypofunction but no single test has sufficiently high specificity and sensitivity. Categorised questionnaires and unstimulated whole saliva flow are valuable. The causes of xerostomia are numerous, of which the principal are, drug or radiation induced xerostomia and primary an secondary Sjögren's syndrome. Treatment calls for good hydration, optimal oral hygiene and prophylaxis of candidosis. All unnecessary medications must be avoided. Oral pilocarpine is the only drug which had demonstrated beneficial effects if no contraindications exist.