The new German laws dealing with protection against infectious diseases (Infektionsschutzgesetz of 1.1.2001) have reconfirmed the importance of microbiology as a basic science and infectiology as a multi-disciplinary clinical discipline. Concerning dermatological diagnosis and therapy, the implementation of molecular biological techniques has a decisive influence. The discovery of new (e.g. Helicobacter pylori) and the better detection of known organisms (e.g. Chlamydia, Borrelia) suggested findings in questions of causality and therapeutic developments. Concerning the infections of the skin this synopsis provides the state of the art of diagnostic process and treatment in mycology, bacteriology and virology.