An explanatory framework, referred to as the attitude/social influence/self-efficacy-model (ASE-model), was utilised to explain future self-reported adherence of adolescents to daily inhaled prophylactic asthma medication. The objective was to investigate the long-term influence of these earlier reported cognitive variables and other psychological and medical determinants on self-reported adherence 1 year later. Data were collected, via a questionnaire, from 86 adolescents with asthma (aged 11 through 18 years) recruited from outpatient clinics. Adherence was assessed by asking the patients to give themselves a report mark for adherence. The results of the multiple regression analyses showed that the three major ASE-variables were predictors of self-reported adherence to a moderate degree (R(2)=0.21). Previous self-reported adherence was found to be the best predictor of self-reported adherence to prophylactic asthma medication 1 year later (R(2)=0.45). The results of this study could be useful in the development of interventions to enhance adherence to asthma medication. In future, such interventions should focus on feelings of shame about having asthma and promoting healthy habits, such as adherence to medication.