Oral malodor has many etiologies and is a clinical problem for many people. This paper reviews the causes and management of oral malador. In the majority of cases the problem has been shown to originate in the oral cavity. Oral malodor, a generic descriptor term for foul smells emanating from the mouth, encompasses ozostomia, stomatodysodia, halitosis (both pathological halitosis and physiological halitosis) and fetor oris or fetor ex ore. These latter terms, in turn, denote different sources of oral malodor. All conditions that favour the retention of anaerobic, mainly gram-negative, bacteria will predispose for the development of bad breath. In addition to periodontal pockets, the most important retention site is the dorsum of the tongue with its numerous papillae. During the night and between meals the conditions are optimal for odour production. Systemic pathological states, such as diabetes mellitus, uremia and hepatic diseases, induce metabolic products that are detectable as oral smells. It is always easy to recognize halitosis, but identifying the exact cause is more complex. The clinical labelling and interpretation of different oral malodors both contribute to the diagnosis and treatment of underlying disease. Treatment is directed at the underlying cause.