Abstract : The object of Mastication is to crash food and form a swallowable food bolus. To comprehend masticatory function, it is essential to understand food behavior during mastication. However, there are almost no reports available there of. The purpose of this study was to observe food behavior after food crushing and consider the association between food behavior and chewing patterns. I designed a new method to estimating food behavior. Peanuts, which were chewed, were gathered separately from buccal side and lingual side after varying numbers of chewing strokes, and then the amount and the degree of crushing of each peanuts was measured. As subjects, twenty case of chewing sides were selected and food behavior and chewing patterns were measured. The results were as follows: 1. As mastication proceeded, the amount of broken peanuts on the buccal side decreased significantly, and those on the lingual side increased gradually. In addition, the degree of crushing was higher on the lingual side than on the buccal side. 2. Food behavior was influenced by chewing patterns. The amount of peanuts on lingual side was greater and the degree of crushing was less in case of Type…ź(compound type)than Type… (grinding type) and Type…ˇ(chopping type).