Phase 2. During the second phase of the study, subjects will be instructed to reduce their controller medication (inhaled corticosteroid alone or combined inhaled corticosteroid with long acting beta 2 agonist) by 50% e.g. from 4 puffs daily to 2 puffs daily. Subjects will log on to their website daily for 4 weeks or until they experience a mild exacerbation (see definition below). If they experience a clinical exacerbation, they will be instructed to return to the hospital site where repeat blood, urine, exhaled air and sputum testing will be obtained (Visit 3a). They will be instructed to increase their controller medication and to continue with the increased steroid phase of the study. Those not experiencing a clinical exacerbation will return to the hospital site at the end of the four weeks (Visit 3b). They will have repeat blood, urine and sputum samples and will then be instructed to eliminate controller medication for four weeks or until they experience a clinical exacerbation. Those experiencing a clinical exacerbation will be treated as outlined above. Those continuing to experience clinical good control will be brought back at four weeks for repeat blood, urine, exhaled air and sputum analysis (Visit 3c). Throughout the 4-8 week period of inhaled steroid withdrawal, patients will be asked to save a urine sample three times weekly. These samples will be stored in pre-labeled containers in their freezer until picked up by the study coordinator at weekly intervals.