To investigate the background of the environment which induces oral mucosal lesions, people who lived in 3 different regions (the farm village, industrial city, and suburb farm village of city) of Northern Jiling in China were clinically examined. Clinical diagnoses were based on WHO criteria. The results were as follows:
1. People who lived in the investigated regions had the habit of smoking cigarettes, but few with leukoplakia were found.
2. The food custom was different among the 3 regions, and many people who lived in the industrial city had the food custom of eating meat.
3. As an oral environment, many people who lived in the industrial city had treated teeth.
4. As for the prevalence of oral mucosal lesions, people who lived in the suburb farm village of city were highest, and the type of oral mucosal lesions varied among the 3 regions.
5. The relation between age/sex and the prevalence of oral mucosal lesions was not evident in all 3 regions.
It was suggested that the social environment and living environment are the important factors that induce oral mucosal lesions, and the oral environment also influences the incidence of oral mucosal lesions. It is conceivable that an epidemiological study on oral mucosal lesions at the local community is useful to investigate the etiology.