Asthma is characterized by airway inflammation, hyperresponsiveness, and remodeling, which are responsible for the variable airway obstruction and respiratory symptoms. Although a number of anti-asthma drugs have been developed, none has succeeded in managing symptoms and underlying airway inflammation as effectively as corticosteroids. However, systemic effects of the drugs were a major obstacle to use them in asthma therapy. A significant breakthrough in asthma therapy occurred when corticosteroids became available as inhaled preparations, reducing the potential for systemic effects while achieving excellent therapeutic efficacy. The first inhaled corticosteroid (ICS) having such characteristics was beclomethasone-17α, 21-dipropionate, which was introduced in the early 1970s. With growing information on their efficacy and the recognition of chronic inflammation as a fundamental component of asthma, ICSs have become the cornerstone of asthma therapy since the early 1990s. The potent anti-inflammatory effect of ICSs seems to be resulted mainly from the reduction of the number and activation of inflammatory cells in the bronchial mucosa and through their inhibitory effects on the synthesis of various mediators and cytokines. In addition, the airway selectivity is thought to come from a high hepatic first-pass inactivation rate of the drugs. A number of ICSs are currently on the market, and some drugs are available as the combination of an ICS and a long-acting beta2 agonist in a single inhaler. The present paper comprises a short background behind the development of ICSs, their pharmacologic and clinical profiles, and the current positions in asthma treatment.