People with haemophilia have been infected by HIV through blood products required for the treatment of their bleeds. In a recent study in Scotland their knowledge of HIV/AIDS and their behavioural changes were explored. It was found that people with severe haemophilia were better informed about HIV and AIDS than the mildly/moderately affected, but only the knowledge of precautions in mildly/moderately affected patients was positively associated with their change of sexual practices. Mildly/moderately affected patients, who were less at risk of contracting HIV, reduced their treatment more than the severely affected patients. Only one third of patients applied safe-sex practices and a greater proportion of those who did not were single men, some of them HIV antibody positive. KEY WORDS: Haemophilia, HIV, AIDS, sexual knowledge, sexual behaviour, condom use.