In recent years there has been an increase in imported tropical diseases in Switzerland. Travellers to the tropics are often inadequately or not at all informed about the dangers and possible prophylaxis of infection. This is true for malaria, of which 207 cases covering the years 1974 to 1976 are studied. Most involved were people between 21 and 30 years old. The main infections (71%) come from African countries. Plasmodium falciparum was found somewhat more frequently than P. vivax. Only a seventh of those infected took chemoprophylaxis regularly. Very many took irregular prophylaxis, while scarcely a third ever took an antimalarial drug. All the severe cases were in this group. A review is conducted of aspects of malaria in Switzerland, a country where the disease is not endemic. However, as it can be brought in at any time from tropical areas, it must be considered in the diagnosis of various clinical pictures. As the characteristic course of the fever is rare and onset of the disease often follows later than a month after the return from the infection area, malaria is only recognized late. The diagnosis is nevertheless relatively easy if the possibility of malaria is borne in mind.