Asthma is a chronic inflammatory disorder that can lead to progressive, potentially irreversible declines in lung function in some patients. Asthmatic inflammation develops when the sequential interaction of inflammatory cells with resident cells generates a cascade of events that contribute to the chronic inflammation and clinical manifestations associated with the disease, including further inflammation, airway smooth muscle spasm (bronchospasm), airway mucus secretion, airway edema and narrowing, and bronchial epithelial damage. Because of the chronic, progressive nature of asthmatic inflammation and the early age of onset, the ability to evaluate inflammation in children would be useful. Several procedures that quantify inflammatory mediators (in peripheral blood, induced sputum, bronchoalveolar lavage fluid, and bronchial biopsies) have shown potential usefulness in the evaluation of and the monitoring of disease severity in children (and, by extension, adults) with asthma. The authors suggest that further research needs to be devoted to the elucidation of when the inflammatory process starts and how it changes over time, to the determination of whether the inflammatory process is the same in all patients with wheezing, regardless of the stimulus, to the definition of the relationship between atopy and asthma, and to the establishment of the usefulness of testing for inflammatory markers to help identify individual asthmatic phenotypes, to evaluate disease severity, to measure therapeutic response, and/or to predict potential outcomes.