From May 1985 to July 1988, 11,445 German residents who had travelled to Africa filled in a questionnaire during the return flight and a second questionnaire sent to them 3 months later. 92.6% of the travellers had been on holiday and 99.3% of these holiday-makers were aware of the risk of malaria. Before and during their stay in the tropics 10,955 travellers (95.7%) had taken the chemoprophylaxis correctly, though in some instances the drugs prescribed were not in accordance with the guidelines existing at the time. However, 3227 of them (35.5%) discontinued the drugs too early, i.e. less than four weeks after their return. Only 4.3% of the travellers had taken proper precautions against mosquito bites. In view of the ever increasing numbers of people travelling to countries where malaria is endemic, doctors and travelers should be provided with more information and should be given more consistent advice on malaria prophylaxis.