Imported infectious diseases being seen more often in consequence of intensive human contacts with developing countries through labourers and tourists, but also in consequence of immigration and of import of exotic diseases and of food, favoured by the quick air traffic, can be divided into 5 groups: 1. Imported diseases from the tropics (exotic diseases) 2. Imported agents from the tropics with human infection in the native country 3. Re-importation of diseases which were eliminated in the homelands 4. Diseases which are as well imported as also native 5. Single disease importations from neighboured countries. The imported infections are discussed systematically, caused by viruses, rickettsias, bacteries, protozoes, fungi, and followed by references to statistics, laboratory infection reports, questions of insurance. Imported diseases of the future are especially mentioned. Knowledge of the tropical infections as a main danger for our "civilized" world should be part of the medical training, since imported infectious diseases cause an epidemiologic challenge in the modern picture of communicable infections.