Bad breath is a condition that has health and social implications. This paper provides a comprehensive review of the classification of halitosis, it's etiology, it's prevalence, diagnosis and treatment strategies for the condition. Halitosis is affecting about 25-30% of world's population. It includes categories of genuine halitosis, pseudo-halitosis and halitophobia. It is believed that in 80-90% of cases halitosis origins in the oral cavity and the most common causes are: gingival pathologies, caries and poor oral hygiene. Extraoral sources of halitosis are responsible for 10-20% of all cases and are caused by poor diet, alcohol abuse, tobacco smoking, certain drugs and diseases of other parts of digestive tract as well as some systemic conditions. Diagnostics of halitosis includes subjective methods (examiner's sense of smell) and objective methods (instrumental analysis). Simple, subjective examination is considered a "golden standard" in clinical practice. In case of pathological halitosis identifying the direct cause of halitosis is essential. After excluding, or after successful treatment, of all oral pathologies, in case of remaining fetor ex ore identification and treatment of halitosis often requires multidisciplinary approach. Many unknowns remain in causes and mechanisms of halitosis. It can significantly impair quality of life, social interactions, lead directly to depression,low self-esteem or other mood disorders, therefore it is important to properly identify, treat and continue research on halitosis.