In stomatology, salivary function and dysfunction are seldom discussed in their biological and psychological aspects; too often, the terms are mistakenly used as synonyms. The importance of identifying these conditions not only involves direct therapeutic implications, as it can additionally influence global and systemic buccal conditions, as well as modify tissue response and psychological adaptation to dental, periodontal and prothesis therapy as currently performed in daily practice. The physiopathogenesis, etiology, the local and general clinical repercussions, as well as those on behavior, the methods of clinical evaluation and treatment/handling of hyposalivation and xerostoma, are presented and discussed.