As the pathophysiologic process of asthma has become better defined, new molecular targets for treating asthma have emerged. Resident airway cells, circulating leukocytes, and various cell-derived mediators and cytokines contribute to the inflammatory events of asthma. New therapeutic approaches to moderate to severe asthma currently in clinical development include antibodies to IgE and interleukin-5, a soluble receptor that would sequester interleukin-4, cytokine and chemokine receptor antagonists, and phosphodiesterase type 4 inhibitors. Adhesion molecules, which are involved in the migration of inflammatory cells into lung tissue, are also important targets for new antiasthma therapies. Because of researchers' focus on specific pathologic processes and molecular targets, the adverse effects of new agents may be minimized. Also, the longer duration of action of some of the new agents allows weekly to monthly dosing, which may well enhance patient compliance.