Immunopharmacology as a field of scientific endeavor had its origins more than thirty years ago in the application of antibody-based techniques to assays of hormones and drugs in tissues and body fluids. More recently, the field has been redefined to include a primary focus on the immune system as a target of xenobiotic action. Advances in the field of immunology have made it apparent that the immune system, like other organ systems, declines in its function as a result of aging, viral infections like AIDS, and other immunotoxic influences, giving rise to secondary immunodeficiency. Deficiencyof the immune system in turn leads to infections, autoimmune diseases, and an increased incidence of certain cancers. The notion of treating the failing immune system is relatively new; however, more than a decade of research on cancer and AIDS has created the burgeoning new clinical field of immunotherapy. Immunopharmacology then stands as the preclinical and clinical science of immune manipulation. As such, like its parent field of pharmacology, it includes within its scope basic studies of immune mechanisms as they relate to the pathogenesis of inflammation and immunologic disturbances. As with pharma- cology, the perspective is always a therapeutic one. Studies of immune and inflammatory processes emphasize the use of pharmacologic probes and drugs to elucidate the underlying biochemical pharmacology.