Following major surgical interventions or severe trauma a dramatic depression of humoral and cell-mediated immune functions has been reported. This immune dysfunction represents a major determinant of increased susceptibility to septic complications and the ensuing multiple organ failure syndrome. This paper reviews the reported immunological alterations following major trauma or surgery. Furthermore, an overview of the therapeutic immunological interventions which have been studied or that are under clinical investigation is given. Despite the dramatic progress in the field of surgical immunology we still do not possess the "magic bullet" for the optimal stage-oriented treatment of trauma-induced immune dysfunction. Clinical research, therefore, has to focus on the development of methods to timely determine the state of activation of the host immune system. This will then enable us to design adequate immunotherapeutic interventions for the treatment of immunosuppression in surgical patients.