Theatre is now widely used in HIV and AIDS education for young people. However, research concerning its effectiveness has largely been conducted without using comparison or control groups and there is little evidence that other types of intervention are more or less effective. The present study was designed to measure the effects of a theatre production on HIV knowledge, attitudes and risk behaviour of young people compared with that of a standard health education seminar which used group work techniques. Both interventions were designed for young people between the ages of 12 and 18 and held in 10 youth projects in socially deprived areas of Glasgow. Five youth projects were randomly assigned to each intervention. All participants were asked to complete a self-administered HIV knowledge, attitude and behavioural questionnaire immediately before and after the event and 2 months later. Research focus groups were also used. A total of 35 young people attending the standard seminars completed three self-administered questionnaires, and 18 participated in all three focus groups. Forty-two young people attending the theatre performances completed three self-administered questionnaires and 16 participated in all three focus groups. There was little impact on the knowledge and attitudes of either audience, although there was some evidence of attitudinal change among those exposed to the health education discussion session. More of the theatre group reported a behavioural change 2 months after attending the play but only in relation to buying and carrying condoms. It is uncertain whether this led to safer sex practices. This study does not support the view that theatre in AIDS education has a significant impact on HIV knowledge, attitudes and risk behaviour.