One of the goals of asthma therapy is to maintain control of symptoms without producing unwanted effects from asthma medications. Corticosteroids are the mainstay for intractable chronic asthma, but their long-term use in high doses is limited by the risk of significant adverse effects. Therefore, a drug that may find a place as an adjunct to regular corticosteroid therapy, as a corticosteroid-sparing agent, or as an alternative to corticosteroids is needed. In this context, drugs, such as cyclosporin, that inhibit T-lymphocyte activity are receiving increasing attention since the hypothesis that activated T-lymphocytes play a central role in the pathogenesis of asthmatic airway inflammation has emerged. The results of recent clinical trials of cyclosporin provided a gleam of hope for the treatment of steroid-dependent or steroid-resistant asthma. However, it would be premature to consider the addition of this type of drug to the armamentarium of antiasthmatic drugs before the results of comparative studies to weigh the benefits against serious long-term side effects are obtained. Nonetheless, the data of those trials may encourage development of other, safer drugs that suppress T-lymphocyte function.