Guidelines for asthma management have proposed that initial treatment should be based on assessment of asthma severity. The treatments proposed for different degrees of asthma severity are essentially estimates of the intensity of treatment needed to achieve asthma control. Responsiveness to treatment is heterogeneous, however, even among asthmatic patients with asthma of similar severity. This heterogeneity calls attention to the importance of assessing asthma control and adjusting treatment accordingly. Application of a guidelines-based approach to asthma management thus requires general agreement on what is meant by severity, control, and responsiveness and requires further an awareness of asthma as causing symptoms and functional impairment in the present and also as causing risk of adverse events in the future.