Eosinophilic ulcer of oral mucosa (EUOM) is a nonspecific clinical appeara nce, which appears to be frequently unrecognized or misdiagnosed usual ly as squamous cell carcinoma (SCC), especially rnin old patients. It i s a rare self-limited benign ulcerative disease, and it is characterized with t he infiltration of eosinophilic leukocytes mixed with other inflammatory cells, 1,2 such as th e mitotically active large mononuclear cells with round or ovoid pale nu cleus. This cell type, often interpreted as a histiocyte, confounds the histolog ic evaluation and occasionally leads to the erroneous diagnosis of lymphohistioc ytic malignant condition. Although it has assumed that trauma is an important et iologic factor, the exact pathogenesis remains unclear.3 The morbidity of this disease is low and there are few Chinese literatures about it,4 so it is n ecessary to pay more attention to it. In this article, 3 out of 5 cases of EU OM are misdiagnosed as SCC, and we will report the records in order to identify it from SCC well.