In England and Wales, gay men currently make up the largest group o f diagnosed cases o f A IDS and o f individuals reported as H I V antibody positive. For the immediate future, therefore, they w i l l remain an important group for any preventive strategies. A n understanding o f the beliefs, attitudes and other social factors that influence the sexual behaviour o f gay men in response to AIDS is an essential prerequisite for the development o f appropriate kinds o f health education, and in this respect an impressive array o f explanations has begun to emerge from behavioural research in the United States. This chapter examines the research efforts that have been made so far to understand the social processes whereby individuals have made marked changes in their lifestyles. A t the same time, many research challenges remain and there are limitations and problems w i th many o f the studies that have so far been carried out. These w i l l need to be examined as social research into the behavioural aspects o f AIDS gets under way in Britain.