The incidence of syphilis, an infectious disease caused by Treponema pallidum, is low worldwide. The knowledge of its symptoms is however important, since the infectivity is high and therapy is comparatively easy. The first feature of an infection is the chancre, which is nearly always located in the genital region. In half of the infected patients after 8-12 weeks, if untreated, a generalisation takes place, during which the bacteria affect all organ systems. At first the skin diseases are most prominent; in long-term disease (late syphilis) symptoms of the central nervous system and the cardiovascular system become more relevant. In the chancre the infectious agent may be proven natively, but not in a culture. At about 3-6 weeks after infection specific serum antibodies may be proven with very sensitive and specific methods. Mainly the TPHA and FTA tests are used. These tests allow a reliable diagnosis to be made also in cases with ambiguous clinical features. The treatment of syphilis is performed by using parenteral depot penicillins for 14 days. It may also be applied as post-exposure prophylaxis. Specifics of the course have to be take into consideration in cases of coexisting HIV infections and neurosyphilis. The disease has a favourable prognosis, when treatment starts early enough.