The widespread use of inhaled corticosteroids (ICS) for the treatment of persistent asthma, although highly effective, may be associated with both systemic and local side effects. Systemic side effects of ICS have been extensively studied. In contrast, relatively few studies have been performed to specifically evaluate local side effects of ICS. These local side effects--including oropharyngeal candidiasis, dysphonia, pharyngitis, and cough--are generally viewed as minor complications of therapy. However, they can be clinically significant, affect patient quality of life, hinder compliance with therapy, and mask symptoms of more serious disease. Local side effects result from deposition of an active ICS in the oropharynx during administration of the drug. Numerous factors can influence the proportion of an inhaled dose that is deposited in the oropharyngeal cavity, including the ICS formulation, type of delivery system, and patient compliance with administration instructions. Therefore, the incidence of local side effects can vary widely. The goal in developing a new ICS is to include key pharmacologic characteristics that reduce oropharyngeal exposure to active drug while maintaining efficacy comparable with currently available ICS.