This paper presents the etiopathogenesis, symptomatology, evaluation and treatment of mouth dryness. Xerostomia affects 1-29% of the population, mostly women. It is observed in geriatric patients and in individuals using certain medications, those subjected to radiotherapy of the head and neck region or affected with autoimmune conditions. The main signs of xerostomia include the impression of a dry mouth, problems with food ingestion and dryness of the oral mucosa and skin. Evaluation is based on structured interviews (the Fox test) and determinations of unstimulated and stimulated salivary volume. The signs of xerostomia can be attenuated with saliva substitutes, cevimeline or malic acid. Only palliative treatment of this condition is available at present. Untreated xerostomia significantly impairs the quality of life, which can potentially lead to depression.