Halitosis affects a large numbers of populations, and it has a significant impact on our interpersonal relationship and social life to those who suffer from it. Halitosis may originate from pathological, physiological or psychological factors. To eliminate halitosis, recognizing the etiologies of halitosis is important. Volatile sulfur compounds (VSCs) being the main cause of halitosis has been proved. We can estimate severity of halitosis and outcome of treatment by measuring concentration of VSCs. Moreover, some people suffering from periodontal disease are bothered by halitosis. This review illustrates the association of microorganism with halitosis. The relationship between halitosis and periodontal disease is further assessed and equipments for measurement of halitosis and VSCs are mentioned. Additionally, treatment of halitosis is also discussed.