The causal role of immunoglobulin E (IgE) in triggering the cascade of biochemical events leading to allergic disease is well established. Treatments that selectively inhibit IgE activity are a logical approach in managing the allergic response. One such strategy utilizes rhuMAb-E25, a recombinant humanized IgG(1) monoclonal anti-IgE antibody, which binds to IgE. This anti-IgE antibody binds at the same epitope site of IgE that binds to FcvarepsilonRI and is thus non-anaphylactogenic. By binding to IgE and removing it via immune complex formation, the pool of IgE available to interact with mast cells and basophils is thereby reduced and the allergic response is attenuated. The clinical safety and efficacy of rhuMAb-E25 demonstrated in phase II studies of allergic asthma will be outlined.