More than 75% of all Dutch haemophiliacs participated in a mail survey that included a section on acquired immunodeficiency syndrome (AIDS). Although no cases of haemophilia-related AIDS had been reported in the Netherlands at the time of our survey, the threat of AIDS had caused considerable anxiety among Dutch haemophiliacs. This had led almost a third of the patients to change their therapy schedules. These changes were mostly not beneficial and possibly counterproductive, since they were not likely to reduce the risk of human immunodeficiency virus (HIV) infection. Measures that were advised to prevent HIV transmission, such as the use of condoms, were seldom carried out, even by the 17% seropositive individuals. We conclude that an increase in the informational efforts towards the patients is called for to avoid ill-advised treatment changes and to enhance preventive behaviour.