Although research in asthma has concentrated on complex proinflammatory mechanisms, it is likely that defective expression of cytokines that inhibit allergic inflammation, such as interleukin 10, interleukin 12 and interferon gamma, might also be important, particularly in determining disease severity and persistence of inflammation in the airways. Therapy based on these cytokines might also be useful, with the advantage that it restores the balance of endogenous cytokines. We discuss the therapeutic potential of these and other inhibitory cytokines in the treatment of asthma, particularly in patients with severe disease that is poorly responsive to conventional therapy, or as a disease-modifying treatment when used early.