Because of increases in the morbidity and mortality associated with asthma, coupled with shrinking health care resources, the costs associated with therapy with beta 2-agonists in metered-dose inhalers (MDIs), the most frequently used class of therapeutic agents, were examined. Recent recommendations suggested a change in drug therapy for asthma, away from theophylline and toward patient-administered MDIs containing beta 2-agonists or corticosteroids. These recommendations are expected ultimately to reduce overall costs by decreasing morbidity due to asthma and by reducing hospital services. Furthermore, differences exist among the various beta 2-agonists. For example, for patients treated with albuterol inhalers, total asthma drug costs, the costs of additional asthma drugs, and hospital costs were lower than those for patients treated with metaproterenol inhalers, despite the higher acquisition cost of albuterol. Using the maximum recommended number of daily inhalations and standardized pricing data, the daily costs of nine individual beta 2-agonists in MDIs were calculated. These varied from $0.61 for albuterol to $1.28 for pirbuterol, but would be lower for patients who required fewer daily inhalations on an as-needed basis. In addition, agents that can be dosed as needed (i.e., albuterol) are likely to be more cost-effective choices for formularies than more expensive new bronchodilators such as salmeterol, which must be given twice/day on a regular basis.