Syphilis is a sexually transmitted infection caused by the spirochaete Treponema pallidum. Syphilis re-emerged worldwide in the late 1990s, and hereafter increasing rates of syphilis were seen also in Denmark. Currently, around 700 cases are diagnosed yearly in Denmark, and syphilis is mainly encountered among men, who have sex with men. However, because of the risk of congenital infection screening of pregnant women has been introduced. Syphilis gives rise to highly variable symptoms such as chancre, skin rashes and fever or latent infection. The recommended treatment is intramuscular administration of penicillin.