Traditionally, bronchodilation with theophylline has been a mainstay of treatment for persistent asthma. Current treatment guidelines, however, call for reliance on anti-inflammatory therapy and recommend that theophylline and other long-acting bronchodilators be reserved for adjunctive therapy for patients not well controlled on anti-inflammatories alone. OBJECTIVE: To estimate the association between type of asthma maintenance therapy (anti-inflammatory versus bronchodilator) and total costs of asthma treatment. METHODS: Patients were selected from the Asthma Outcomes Registry cohort if they had received either anti-inflammatories (inhaled steroids or cromones) or long-acting bronchodilators (theophylline, long-acting beta-agonists, or ipratropium), but not both, for at least one year prior to study entry. Oral steroid dependent patients and those with incomplete cost data during the baseline and follow-up intervals (365 days before and after their enrollment in the Registry, respectively) were excluded from the analysis. The effect of anti-inflammatory versus bronchodilator therapy was assessed by comparing the change (follow-up minus baseline) in the logarithm of total costs of asthma care. RESULTS: 446 patient met criteria for study inclusion, including 351 treated with anti-inflammatories and 95 treated with bronchodilators. Geometric mean costs during the baseline year were similar in the anti-inflammatory and bronchodilator groups ($358 and $351, respectively). In the follow-up year, geometric mean costs declined by $149 (to $209) in the anti-inflammatory group compared to an increase of $19 (to $340) in the bronchodilator group (p<0.0001). This treatment effect was essentially unaltered after adjustment for study site, age, sex, smoking, and comorbidity. CONCLUSION: These findings add support to current guidelines recommending reliance on anti-inflammatory therapy to control asthma. The emergence of new therapeutic agents to control inflammation may continue to reduce the costs of treating this important disease.