This article reviews an emerging area of research on patients with asthma: namely, illness perceptions and their relationships with various aspects of outcome. The article briefly introduces the Common Sense Model, outlining the relevance of how "lay" patients conceptualize symptoms, illness, and treatment. On the basis of a comprehensive literature search, nine empirical studies illustrating the relationships between illness perceptions and outcomes are discussed. It is concluded that further research should focus on assessing asthma-specific illness and treatment beliefs. Also, given the effects of intervention studies in illness perceptions in other patient categories, it is recommended that serious consideration be given to intervention studies focusing on eliciting and changing illness perceptions in asthma patients, especially in those whose self-management seems to be inadequate.