In this analysis, we sought to determine factors that predicted the level of asthma knowledge in a sample of adolescents with asthma and their parents. Eighty-five young people aged 10-24 years attending tertiary care asthma clinics and 46 of their parents answered validated respiratory and asthma knowledge questionnaires. Older adolescents were more knowledgeable about asthma than were younger adolescents (r=0.36, p=0.001). Young people with severe asthma (p=0.015) scored higher on the asthma knowledge questionnaire than those with mild/moderate asthma. Asthma knowledge among young people was related to that of their mothers (r=0.47, p=0.014), however, only age and the asthma knowledge of fathers significantly predicted adolescent asthma knowledge. Adolescents develop increasing autonomy for asthma self-management as they mature, but parents remain an important source of information about asthma for young people.