Current guidelines for asthma treatment do not recommend daily maintenance therapy in patients with mild intermittent (step 1) asthma. However, because there is increasing evidence that airway inflammation is present even in this patient group, maintenance anti-inflammatory therapy may be considered. We investigated the clinical impact of regular treatment with the inhaled corticosteroid beclomethasone dipropionate and the leukotriene receptor antagonist pranlukast in the patients concerned. The study was a randomized, controlled, parallel-group, multicenter trial. Eighty-five symptomatic patients with newly diagnosed mild intermittent asthma having normal pulmonary function were assigned beclomethasone or pranlukast for 8 weeks. Then, these medications were stopped for the next 16 weeks. Main outcome measures were asthma symptoms, pulmonary function, and airway inflammation. Treatment with beclomethasone and pranlukast significantly increased forced expiratory volume in 1 second and peak expiratory flow from baseline and decreased asthma symptom scores and sputum eosinophil counts and eosinophil cationic protein contents. After discontinuation of the treatment, symptom scores remained unchanged, but pulmonary function and airway inflammation were aggravated and then returned to the baseline levels. Therefore, maintenance therapy with inhaled corticosteroid or leukotriene receptor antagonist can provide further improvements in asthma symptoms, pulmonary function, and airway inflammation, and discontinuation of the therapy causes worsening of asthma, indicating that stopping or interrupting anti-inflammatory therapy may not be advisable in patients with symptomatic mild intermittent asthma.