Controlling the AIDs epidemic may depend largely upon health education aimed at adolescents. A number of approaches have been applied to human immunodeficiency virus (HIV) preventive behaviour in adolescents, including the health belief model (Becker, 1974), protection motivation theory (Rogers, 1983), and the theory of planned behaviour (Ajzen, 1985, 1991). Since sexual behaviour is heavily influenced by emotions, a possible shortcoming of these models is that little attention is given to affective processes. In this study we investigated the role of anticipated, post‐behavioural, affective reactions to (un)safe sexual behaviours in the context of the theory of planned behaviour (TPB). The results showed that anticipated affective reactions such as worry and regret predicted behavioural expectations over and above the components of the TPB. The implications for our understanding of adolescent sexual behaviour and for campaigns aimed at the reduction of risky sexual practices will be discusse