Aspiration of acid to the airway causes airway inflammation, and acid stress to the airway caused by gastroesophageal reflux disease (GERD) has been known as a potential mechanism of deteriorated asthma symptoms. However, the efficacy of the acid suppressive drugs, H(2)-receptor blockers (H(2) blocker) and proton pump inhibitors, on asthma symptoms and pulmonary functions remains controversial. We therefore designed the randomized prospective study to determine the efficacy of an H(2) blocker (roxatidine, 150 mg/day) and a proton pump inhibitor (lansoprazole, 30 mg/day) on asthma symptoms of 30 asthmatic patients with GERD. These patients were divided in the two groups (15 patients for each group) and treated with either roxatidine or lansoprazole. The diagnosis of GERD was established by the method of Los Angeles classification including mucosal minimum change of Grade M and questionnaire for the diagnosis of reflux disease (QUEST) score. The efficacy of acid suppressive drugs was evaluated by peak expiratory flow (PEF), asthma control questionnaire (ACQ) that evaluates the improvement of asthma symptoms, and forced expiratory volume in 1 second (FEV(1.0)). Lansoprazole, but not roxatidine, significantly improved PEF and ACQ scores (p < 0.05) with the improved QUEST scores. However, these acid suppressive drugs did not change the pulmonary function of FEV(1.0) in asthmatic patients. In conclusion, treatment with a proton pump inhibitor, lansoprazole, appears to be useful in improvement of asthma symptoms in asthmatic patients with GERD.