To compare the efficacy of combination therapy of montelukast plus low dose inhaled budesonide and single therapy of medium dose inhaled budesonide on asthma control such as inflammatory markers and clinical indicators and to compare treatment response according to leukotriene related genotypes in elderly patients with asthma

Inclusion Criteria:

• Patients aged 60 - 75 years
• Patients diagnosed with asthma (NIH, 2007) over six months ago
• Patients maintaining monotherapy of low dose inhaled budesonide (pulmicort 400µg/day or ciclesonide 160 µg/day or fluticasone 250 µg/day) or combination of low dose inhaled budesonide and LABA (Seretide® 250 µg/day or Symbicort® 320 µg/day ) for over a month before the participation in this trial
• Patients not reaching 'well controlled asthma status' with four-week monotherapy of low dose inhaled budesonide (Pulmicort 400 µg/day)
• Patients who sufficiently listen to the purpose and content of this trial and the properties of investigational products and voluntarily agree with the participation to sign a written consent approved by IRB of Ajou University Medical Center before the participation in this trial

Exclusion Criteria:

• Patients who show a symptom of an acute disease within 28 days before the beginning of this trial (administration of trial medication)
• Volunteers who are found to be unsuitable through screening tests
• Patients with history of hypersensitivity to montelukast or budesonide
• Patients participating in other clinical trial within three months before the beginning of this trial (administration of trial medication)
• current smokers having more than 10PYs of smoking history
• Patients needing administration of a medication which can affect asthma control such as systemic and immunoregulatory drugs (cyclosporin, omalizumab, etc.) due to a disease except asthma