B ackground: The habit of chewing betel quid is a habit that is widespread in East Nusa Tenggara. This habit is often associated with smoking and consuming alcohol. The chewing habit will lead to the manifestation in the oral mucosa such as betel chewer's mucosa, oral submucosa fibrosis, leukoplakia, black hairy tongue, and oral cancer. However, until now this has not been done research that shows the percentage of betel chewer's mucosa on there. Objectives: To determine the percentage of betel chewer 's mucosa in chewers at Penkase and Naioni villages, East Nusa Tenggara. Methods: This research was an observational study with a descriptive cross-sectional design and conducted checks on 40 subjects at Penkase and Naioni villages, East Nusa Tenggara. Results: Found as much as 75% of betel chewer's mucosa in subjects who had habit of chewing, 25% in subjects who had a habit of chewing and smoking, and no lesions betel chewer's mucosa in subjects who have a habit of chewing, smoking, and consuming alcoholic beverages. 50% of betel chewer's mucosa was found in the betel quid chewers with each frequency as much as 1-2x and 3-4x a day. 75% of betel chewer's mucosa in the betel quid chewers with chewing duration of 15 minutes and 25% at betel quid chewers with chewing duration of 5 minutes. Betel chewer's mucosa is found most in betel quid chewers who has been chewing between 15-21 years by 50%, 25% in betel quid chewers who has been chewing for 1-7 years, and 25% on the chewing penyirih for 22-28 years. Conclusion: The appearing of betel chewer 's mucosa lesions related to the frequency , duration , and the old habit of chewing done. The more often and the longer a person doing chewing habit, the higher appearing of betel chewer's mucosa in their mouth.