A questionnaire was given to 56 sexually active girls 12-16 years old, in a juvenile assessment centre or attending a genitourinary medicine clinic. Sexual behaviour, drug use, contraceptive practice and knowledge and attitudes about AIDS were evaluated. The girls were similar in demographic characteristics from both centres and were regarded as one group. Sexual experience ranged from 1 partner ever to 70 clients/week; 19 girls had contracted a sexually transmitted disease at some time. Half had never used a contraceptive. Twenty eight had used illicit drugs, with two girls experimenting with intravenous misuse. Misconceptions about modes of transmission of HIV were common, but most girls knew some basic facts about the virus. Most girls realised they were at risk, were anxious about contracting HIV infection in the future, but had not modified their behaviour in terms of condom usage. This study indicates that high risk adolescents need to be targeted for effective health education in order to modify behaviour patterns which put them at risk of acquiring HIV in the future.