A 45-year-old patient had a progressive ulcer of the tongue. Routine examination, including a biopsy was not conclusive and could not entirely rule out a malignancy. The final diagnosis was made after generalised lesions eveloped, after which specific serological tests confirmed the diagnosis ‘syphilis’. The patient was treated with benzathinbenzylpenicillin and his complaints disappeared. In view of the increasing incidence of this disease remains an important consideration in case of ulcerative or other lesions in the oral cavity.