The aim of this study was to determine the prevalence of self-assessment halitosis and to offer the basic information that establishes a strategy of effective health promotion and to enhance the quality of life. This study performed a questionnaire survey. The questionnaire was filled out by the 362 adults, who lived in Incheon Metropolitan City from May to July, 2010. The data were analyzed using a Chi-square test in the SPSS version 12.0 program. The prevalence rate of self-assessment halitosis was 24.3%. Hypertension, diabetes, medication and inadequate oral hygiene practice were significantly associated with self-assessment halitosis. Other factors of self-assessment halitosis were older age and occupation. As a result, dental professionals have to investigate a systemic disease history thoroughly. And they have to educate regular checkup of oral health and to perform a continuous feedback. The self-assessment halitosis has a negative influence on mental health and social life, so dental professionals must take into consideration about the halitosis.