In developing countries, AIDS is transmitted in essentially the same way as other sexually transmitted diseases. Therefore the spread of AIDS is also associated with travel. Unfortunately, it is still very difficult to assess the distribution of the infection, especially in developing countries, because in these countries often only 10% of the cases are identified and registered. It can, however, be stated that the highest infection rates are found in Central Africa, in some South American cities, and in the Caribbean. Moderately high rates are found in Western Europe, the USA, Canada and Australia. In the Eastern bloc, in Asiatic countries and in the Pacific area, and in considerable parts of North Africa and South America, the pandemic is only just beginning. Sexual intercourse has been found to be the main means of transmission of HIV infection in developing countries. In addition, further risk factors have been identified; venereal disease, and ulcers on the sexual organs. The risk of parenteral transfer is also considerable, because of inadequate testing of blood for transfusion, and the lack of satisfactory facilities for sterilisation. For tourists and development workers, the risk of infection depends very much on their own behaviour when they are overseas. Though the risk of infection is somewhat higher in developing countries, it can clearly be greatly reduced if travellers are adequately informed and are thus equipped to take the necessary precautions.