This is a crossover randomized double blind, placebo-controlled study where the early and late response to allergen inhalation challenge will be compared during two treatment periods, with pemirolast 200 mg bid for 14 (to 16) days and matching placebo, respectively. Non-smoking female and male subjects (n = 12-15) with intermittent atopic asthma, requiring only β2-agonists to treat their asthma, will be recruited. A total of twelve subjects who demonstrate an early and a late asthmatic response to inhaled allergen challenge are required to complete the study for the primary end-point. The sample size is sufficient according to experience from a large number of studies and published power calculations of the model. The effects of pemirolast have never been studied before in an allergen provocation model. Primary variable is the effect of treatment on the mean maximum fall in forced expiratory volume in one second (FEV1) during the early and the late asthmatic reactions induced by allergen. Secondary variables are the effect on mast cell activation and airway inflammation measured as the urinary excretion of metabolites of prostaglandins and other lipid mediators and the percentage of sputum eosinophils, respectively. Tertiary variables are the effect of treatment on airway responsiveness expressed as the provocative dose of methacholine causing 20 per cent decrease in FEV1 (PD20FEV1), as well as biomarkers of airway inflammation in saliva, sputum, exhaled air and blood.