Drug therapy is used to prevent and control asthma, and also to reduce the frequency and severity of its exacerbations, and reverse airflow obstruction. Asthma medications are thus categorized into two general classes--bronchodilators (relievers) and anti-inflammatory drugs (preventers). Short acting beta2-agonists is the therapy of choice for relief of acute symptoms and prevention of exercise induced bronchospasm (EIB). Corticosteroids are the most potent and effective anti-inflammatory medication currently available. Inhaled form is used in the long-term control of asthma. Systemic corticosteroids are used to gain prompt control of the disease when initiating long-term therapy. Long acting bronchodilator used concomitantly with anti-inflammatory medications for long-term control of symptoms, especially nocturnal symptoms. Ipratropium bromide may provide some additive benefit to inhaled beta2-agonists in severe exacerbations. Sustained release theophylline is a mild to moderate bronchodilator used principally as adjuvant to inhaled corticosteroids for prevention of nocturnal asthma. Leukotriene modifiers may be considered as an alternative therapy to inhaled corticosteroids or cromolyn or nedocromil.