SETTING: Asthma is the most common chronic respiratory disease among adolescents; however, very little is known about asthma in this age group. OBJECTIVE: To explore asthma in adolescence using cross-sectional and retrospective representative data. DESIGN: A population-based sample of adolescents was selected from 578 classes in 186 schools of eight metropolitan educational districts in France and invited to complete a self-administered questionnaire (National Adolescent Health Survey [NAHS]). RESULTS: Of 14,278 adolescents selected, 12,466 (87%) participated in the survey. Prevalence of 'ever asthma' was higher among boys, among those in the south and west, among those from French overseas departments, in active smokers, and in those with other allergies, including food allergy. It was lower in adolescents whose mother was a housewife. Puberty was not associated with 'ever asthma'; however, asthmatic boys without signs of puberty usually had more attacks than those with. Severe asthma was associated with early onset and female sex. Asthma medications and consultations did not depend on socio-economic status. Asthmatic adolescents were found to need more health care in terms of medication use, consultations and hospitalisations other than for asthma than other adolescents; this relationship was strongest among severe asthmatics.