Aim: The purpose of this study was to estimate the prevalence of halitosis in an adult Turkish subpopulation and to assess the relationship between halitosis and sociodemographics, self reported halitosis, etiological factors, by employing standardized procedures for measurement of halitosis. Methods: The study included 459 subjects who referred to oral diagnosis clinic of Gazi University Faculty Of Dentistry. The questionnaire including the questions of sociodemographic data, halitosis complaints, oral hygiene practices, extrinsic causes and extra-oral causes. In the clinical examination, dentition and soft tissues were evaluated. Tongue coating status, periodontal index, gingival index and plaque index were recorded. Values for halitosis were assessed by measurement of volatile sulfur compounds (VSC) using portable sulphide monitor. Results: The questionnaire revealed that 46.6% of the subjects suffered from halitosis and females sufferred from halitosis more frequently than males. The prevalence of halitosis was 50.7%. A significant correlation was found between halitosis and tongue coating, periodontitis, gingivitis though PI did not affect halitosis. There were not significant correlations between halitosis and oral hygiene practices, extrinsic causes and extra-oral causes. Conclusion: This study showed that there was a high prevalence of halitosis in the Turkish population and the most important factors that influence halitosis were intra-oral causes.