Current guidelines for the treatment of asthma are based on the fact that asthma is an inflammatory disease and that all forms of persistent asthma, whether mild, moderate, or severe, require treatment with a controller medication to reverse or prevent the underlying inflammation. A patient can be considered to have mild persistent asthma if symptoms occur one or more times a week (but less than daily), if exacerbations are affecting activity or sleep, if nighttime symptoms occur more than twice a month, or if peak expiratory flow or FEV1 is equal to or greater than 80% of the predicted value or has a variability of 20% to 30%. Just one of these clinical features is needed to define the condition. A patient with this condition should be treated with a controller medication that is taken daily; the physician may choose between a low dose of inhaled corticosteroid, nedocromil sodium or cromolyn sodium, or slow-release theophylline. The choice will vary depending on the physician and the type of patient being treated. Data on clinical efficacy and safety support the current position of nedocromil sodium as a primary treatment for mild persistent asthma.