The author has undertaken clinical studies on oral infections in the oral cavity and maxillofacial regions by analyzing 987 patients with infections among 3,921 in-patients hospitalized in the Department of Oral and Maxillofacial Surgery, Seoul National University Hospital past 7 years from 1980 to 1987. The results obtained were as follows: 1. Oral infection as inflammatory disease in dentistry is still very important disease occupying 25.4% of diseases in oral and maxillofacial regions. 2. The high 3 top inflammatory diseases in the department of oral and maxillofacial surgery admitted were odontogenic maxillary sinusitis (37.6%), osteomyelitis (29.1%), and abscess (22.2%) among 14 kinds of oral infections. 3. Anaerobic bacterial infections tend to be increasing since new developed bacterial culture chamber has been used.