During the last years monkeys from tropical countries, especially green monkeys (certopithecus and macacus), were imported. Originally they were used for pharmacological and physiological experiments. Since it has turned out that kidney cells of monkeys are very convenient for breeding pathogenous viruses, millions of monkeys were needed by virological institutes and pharmaceutic firms throughout the world. As the animals are transported by air directly from their home districts to the institutes it is possible that exotic diseases can be imported—the monkeys can be reservoirs as well as carriers. Until now only single cases of diseases transmitted by monkeys are known as e.g. “herpes simiae” and “Rabies”. The “new” disease observed in Marburg, Frankfurt, and Belgrade was the first to occur in an epidemic outbreak.