Eosinophilic ulcers of the oral mucosa represent a rare, self-limiting disease of unknown origin. Single lesions occur typically in the oral cavity or on the lower lip. Characteristically, they have a short history and resolve spontaneously. Diagnosis is verified by the histologic feature of a deep polymorphic inflammatory infiltrate with numerous eosinophils. The clinical aspect shows a usually nontender ulcer with a white or yellowish base and elevated indurated borders or a tumor with central ulceration. Lymphadenopathy is not found. Differential diagnoses include malignant tumors and the primary stage of syphilis. We present three cases recently diagnosed in our department to show the characteristics and the different appearances of the disease. A 74-year-old woman presented with an ulcer at the base of the tongue, a 59-year-old man had one on the lower lip, and in a 48-year-old man the lesion was atypically located at the edge of the mouth. Here we demonstrate the importance of knowledge of the disease, its course, and the characteristic histology to avoid troublesome diagnostic and therapeutic procedures.