Asthma is a complex, chronic inflammatory disease of the lower airways affecting people of all ages. Approximately 300 million individuals are currently suffering from asthma worldwide. The prevalence of asthma is estimated to range from 3% to 38% in children and from 2% to 12% in adults. The disease causes lost school and work days, limitations in daily activities, and sleep disturbances. Lung function impairment also occurs, resulting in decreased quality of life unless disease control is achieved and a high annual financial burden is incurred. Achievement and maintenance of control through assessment of clinical manifestations and future risk has become the aim of treatment over the years. Unfortunately, the desired level of asthma control has not been achieved in a considerable number of regions throughout the world, and the level of control is overestimated by both patients and their parents. This review examines the mortality and morbidity rates for asthma, emphasizes the challenges inherent to control management, and provides data on the tools used to measure control level. (C) 2012 SEICAP. Published by Elsevier Espana, S.L. All rights reserved.