Halitosis is a bad odor in mouth. The etiology of halitosis is multifactorial including intra-oral and extra-oral causes. It affects social interactions in many people. The aim of this study is to investigate an association between recognition group and non-recognition group by evaluating halitosis level and systemic factors. Nineteen participants who visited Department of Periodontology of Seoul National University Bundang Hospital were enrolled. Volatile sulfur a compounds (VSCs) were measured by Oral ChromaⓇ, a questionnaire was requested and oral exam was carried out in all subjects. Female is more sensitive than male for oral malodor. VSCs level of hydrogen sulfide(H2S) and methyl mercaptan(CH3SH) in male is higher than that in female. Participants who gave appeal dry mouth seem to recognize halitosis.