Three independent cross-sectional surveys of public knowledge and attitudes about AIDS were conducted on a representative sample of people aged 15-54 resident in Wales. 1,303 were interviewed in their homes in February 1987, 683 in September 1987 and 676 in March 1988. The results show that most people knew that having sexual intercourse or sharing needles with people with AIDS represented a high risk of catching AIDS. However there appeared to be considerable misunderstanding about the nature of HIV infection such that one in three thought that a man and woman with a single heterosexual partner was at high or moderate risk of catching AIDS. The high level of concern coupled with considerable confusion appears to have contributed to both unnecessary anxiety and prejudice. One in four people thought that kissing or being spat on by a person with AIDS represented a high or moderate risk, and one in six thought that coughing, sneezing and sharing towels, soap, drinking utensils or lavatory seats were routes of transmission. More than 50% of men and 40% of women said that it was their own fault if homosexuals and drug addicts got AIDS and did not feel sorry for them. It is concluded that action to date to limit the spread of AIDS has informed but not yet adequately educated the public. If unwanted anxieties and prejudice are to be diminished, initiatives by government, health services and others must now concentrate on developing understanding about the nature of HIV infection and its spread through more personal education.(ABSTRACT TRUNCATED AT 250 WORDS)