Although human immunodeficiency virus (HIV) infection and acquired immune deficiency syndrome (AIDS) are firmly entrenched in Hong Kong no data are available on the knowledge and attitudes of Hong Kong secondary school teachers and teenage children towards this infection, and their perception of infection control measures currently undertaken by the dental profession to prevent such infectious diseases. Hence a postal questionnaire survey of a total of 2,886 teenagers and 372 school teachers of 21 secondary schools in Hong Kong was conducted. The questionnaire comprised a total of 13 questions divided into two categories; the first, aimed at assessing the respondents' general knowledge and attitudes towards AIDS, and the second related to AIDS, dentistry and infection control. More than half of the students and one quarter of the teachers surmised that HIV infection is equivalent to developing AIDS. Although the great majority of the respondents (85-97 per cent) were aware that HIV can not be transmitted through sharing combs and meals, one in two teachers and one in three students thought that the virus could be transmitted through saliva. A large majority of respondents believed television to be the most, and dentists the least, informative source on AIDS out of a list of eight options. Approximately one half of both groups were concerned about contracting HIV infection during dental treatment and 65 per cent of students and 57 per cent of teachers thought that dentists did not have sufficient knowledge to identify AIDS patients. Finally, more than three quarters of the respondents thought that it would be ill-advised to visit a dentist treating HIV-infected patients.(ABSTRACT TRUNCATED AT 250 WORDS)