Saliva plays an important protective role in the oral environment, and reductions in saliva quantity are known to increase the risk of oral diseases. Importantly, xerostomia or the perception of a dry mouth is now being recognized as an important risk factor for dental diseases. Furthermore, the subjective sensation of a dry mouth is a debilitating condition in itself that impacts on the quality of life of sufferers. With approximately 1 in 5 people reporting some form of dry mouth, and an increasing prevalence in the elderly, it is important for clinicians to have a thorough understanding of this problem. The aim of this paper is to review some of the literature relating to xerostomia in order to provide an evidence based update for clinicians.