The purpose of the pilot study was to know the relationship between halitosis and oral hygine, to examine the difference of the positon of the straw to be placed in the oral cavity by using Halimeter. Fourteen persons that has good health condition without halitosis were participated in this pilot study. They were treated twice prophylaxis and then they had not tooth brushing during two weeks. After two weeks, they were examied to gingival index, plaque index, VSC valuses. The obtained results were as follosws : 1. No significant difference of VSC values were observed during two weeks withoiut tooth brushing. But significant difference of gingival index, plaque index were observed. It was suggested that halitosis was not caused by only plaque, complex reasons(salivary function, stress etc) maybe caused halitosis. 2. Here were significant reduction of VSC values as the depth of plastic straw into the oral cavity decreased (p<0.05)