Syphilis is an infectious disease caused by the organism Treponema pallidum. There has been a dramatic increase in the number of new cases of syphilis in the UK over the past decade. Intra-oral ulceration is often the only presenting feature of the disease, which then enters a latent period. A missed diagnosis can often lead to serious complications and may result in further spread of the disease. Three cases are discussed in this paper with varying clinical presentations of the disease. Such a significant increase of syphilis and its high infectivity require the dental profession to increase their awareness of sexually infectious diseases and the appropriate dental management.