Qat is planted in Yemen and greatest of the republics of East Africa as a normal stimulating from the Catha edulis plant(1)(2). However, Qat chewing spread approximately to totally parts of the world due to improvements in passage and bulk travel of people. Qat naturally accompanying or associated with oral white lesions which arise in the area in the buccal mucosa where the Qat is sited during chewing. Certain of these lesions demonstrate epithelial cytological alterations as acanthosis, hyperkeratosis and mild dysplasia, the danger for emerging white lesions was especially great between Qat chewers who also used tobacco products(3). So this study was conducted to compare the immunohistochemical expression of CLDN1 in different grade of epithelial dysplasia in site of Qat position at buccal mucosa. Material and methods: the study was carried out in 40 individuals of Qat chewers.  The individuals had a mean age of 38.28 years (range 19-65 years). The group comprised 3 females and 37 males. Dysplasia were categorized to (12 mild, 17 moderate, and 11 severe). The mean and standard deviation of area percent of IHC staining was evaluated, (P ˂ 0.05) was considered statistically significant.RESULTS:CLDN1 the greatest mean area of immunoexpression was recorded in the mild dysplasia, whereas the least value was recorded in severe dysplasia. (ANOVA) test exposed that the variance was statistically significant (P<0.000).