Dental clinicians and other health care providers have long been concerned about a variety of infectious agents that may be transmitted within the dental setting. Many infectious diseases, including human immunodeficiency virus, hepatitis, tuberculosis, and syphilis are important both because of their potential transmissibility and because the first manifestations of the disease may appear in the oral cavity. Oral disease as a consequence of primary syphilis is rare. This article details a patient presenting with a labial nodule as her only clinical manifestation of undiagnosed primary syphilis.