The incidence of sexually transmitted diseases recently increased in the United States and Europe due to migration, increase in high-risk behavior, and abandonment of safer sex practices at the advent of antiretroviral combination therapy for human immunodeficiency virus infection. This article presents four cases of primary oral and perioral syphilis with differential diagnoses. It is important to bear this reappearing infection in mind to avoid latent infection. Resembling common oral infections, the primary affect disappears spontaneously, and the infection enters the second stage. The patient remains infected, may further spread the disease, and risks severe organ damage from long-standing infection. The antibiotic cure is inexpensive and safe and spares the patient mucous patches and gumma residuals, apart from severe general sequelae such as thoracic aorta aneurysm and neurosyphilis. However, compliance problems jeopardize clinical and serologic follow-up. The growing syphilis incidence prompts the commemoration of Dr Moriz Kaposi and his dispositive 1891 book Pathology and Therapy of the Syphilis. Moriz Kaposi is acknowledged as one of the heads of the Vienna School of Dermatology, a superb clinician, and renowned teacher.