Asthma is now recognized to be a chronic inflammatory disease of the airways, involving mast cells, eosinophils, and T lymphocytes. Treatment of asthma should therefore be based on anti-inflammatory agents rather than bronchodilators. Choices include inhaled corticosteroids, which are highly effective in all patients, and cromolyn sodium and nedocromil sodium, which are effective in patients with mild asthma. It is likely that the earlier and more widespread use of anti-inflammatory drugs will reduce the unacceptably high morbidity and mortality of asthma and prevent irreversible chronic airflow obstruction in patients with severe disease.