Molecular and Immunological Effects In our view, the introduction of the article leads to the impression that preclinical studies on hyperthermia have already resulted in profound understanding of the molecular basics of hyperthermia. The connections, however, between apoptosis and thermoresistency (not mentioned by the authors) in an organism subjected to elevated temperatures raise a continuum of questions, for example on details of the immunological processes, which can be caused by hyperthermia and which to some extent are mediated by heat shock proteins. In this context, to us the mere phenomenological changes of the white blood cells and of lymphocyte subpopulations observed during hyperthermia may be interpreted too simply. From our own experience we know that it is extremely difficult to extract relevant and independent aspects of the molecular and immunological effects of hyperthermia from investigations which are part of clinical studies, as – among other reasons – the application of hyperthermia, usually, is only part of schemes of treatment involving several different therapeutical modalities. On the one hand, therefore, by our own investigations we can confirm that complex immunological changes like the increase of NK cells in peripheral blood, also mentioned by Feyerabend et al., as well as changes of concentrations of different soluble adhesion molecules and of cytokines take place in patients having undergone whole-body hyperthermia. On the other hand, it is not yet clear to what extend these phenomena differ significantly from those changes which are observed in other stress situations (e.g. polytrauma), thereby reducing the possible significance of these changes for the explanation of the effect of hyperthermia.