Syphilis is a sexually transmitted disease caused by Treponema pallidum. However, there are of hematogenic and vertical transmission. All health care professionals must be aware of the manifestations of this condition, such as oral lesions. This study to analyze and compare four clinical cases of syphilis that were diagnosed based on lesions in the oral cavity with published literature. Four patients with a confirmed sorologic and clinical diagnosis of syphilis were examined, confirmated from manifestation of oral lesions together with analysis of serological laboratory tests and histopathological analyses. Lesions were found in classic sites such as lips, tongue and skin. However, there were also lesions on the hard palate, and labial commissure, which correspond to less than 5% of the syphilis oral manifestations. The practice of unprotected oral sex may result in infection and development of syphilis. The acknowledgment of the oral manifestations of syphilis in all its period of training for health professionals is of basic importance, the association of clinical features, histopathological findings and serological tests are required to complete the diagnosis and correct treatment.