A 25-year-old woman had the chief complaint of recurrent episodes of dyspnea and wheeze. Asthma had been diagnosed at infant years and sometimes experienced asthma attacks. She graduated senior high school and entered technical school in Tokyo. She received fluticasone (400μg daily) but exacerbation continued after she became an office clerk. She returned Kurashiki in October 2001 but had wheeze and asthma exacerbations. She was admitted to our hospital for evaluation and treatment of bronchial asthma on August 2, 2002. After admission, her symptoms subsided within some days. She was treated with montelukast and perilla seed oil-rich supplementation . The number of eosinophils decreased, decrease was observed in leukotriene (LT) B4 generation and in LTC4 generation, and pulmonary function improved following montelukast and perilla seed oil-rich supplementation for 4 weeks. The patient had no exacerbation under treatment and was discharged from the hospital on September 2, 2002. For some patients with persistent asthma, inhaled corticosteroids may fail to achieve adequate control possibly because corticosteroids do not completely inhibit the synthesis and release of cysteinyl leukotrienes (cysLTs) in the lung. Montelukast blocks the interaction of cysLTs with their receptor and resulting downstream events and perilla seed oil-rich diet suppresses LT generation. Combination therapy with montelukast and perilla seed oil-rich diet is more effective than montelukast or perilla seed oil-rich diet alone because of additive effects of montelukast with perilla seed oil-rich diet. We suggest that montelukast and perilla seed oil-rich supplementation are effective options when bronchial asthma patients receive inhaled corticosteroid but exacerbation continues.