The development of objective techniques for the quantitative evaluation of synthesis and production of IgE in man and experimental animals and the sensitivity of basophils in interaction with allergen has made it possible to initiate studies on desensitization on a scientific and objective basis. Several new mechanisms influencing the regulation of antibody formation, including the production of IgE, have recently been discovered, such as suppressor T lymphocytes and autoanti-idiotypic antibodies. Although present empirical methods used for desensitization therapy provide appreciable results, it is to be expected that the emerging immunological knowledge about regulation of IgE production will markedly influence therapeutic approaches in the foreseeable future.