The study describes Danish general practitioners' perception of their own role and their actual behaviour in the prevention of HIV/AIDS. Data collection was carried out by questionnaire and prospective registration of consultations dealing with HIV/AIDS during a two-week period. The results showed that most of the GPs (94%) were of the opinion that GPs should play a central part in the prevention of HIV, and 90% thought that the GP should take the initiative to talk about HIV. The median number of consultations dealing with HIV was two during ten working days (range 0-18), and more than half the GPs (56%) had not themselves initiated a conversation concerning the problem. The conclusion of the study is that there was discrepancy between the GPs' vision of their role in HIV prevention and activities in practice. It is recommended that initiatives are taken to strengthen the GPs' role in AIDS prevention.