The potential for 41.8 degrees C whole body hyperthermia (WBH) to enhance ionizing irradiation and cytotoxic chemotherapy without a commensurate increase in normal tissue toxicity is currently receiving renewed clinical interest. Additionally, WBH may have other biological sequela which may be clinically exploited. In this paper, data are summarized revealing the ability of WBH to induce elevated plasma levels of granulocyte-colony stimulating factor (G-CSF), interleukin-1 beta (IL-1 beta), interleukin-6 (IL-6), interleukin-8 (IL-8), interleukin-10 (IL-10), and tumor necrosis factor-alpha (TNF-alpha) within hours of WBH. Data regarding TNF-alpha shows induction in only a proportion of patients. No induction of C-reactive protein (CRP) or the following cytokines was observed: granulocyte macrophage-colony stimulating factor (GM-CSF), interferon-gamma (IFN-gamma), interleukin-1 alpha (IL-1 alpha), interleukin-2 (IL-2), interleukin-4 (IL-4), interleukin-7 (IL-7), interleukin-11 (IL-11), interleukin-12 (IL-12), macrophage-colony stimulating factor (M-CSF), and macrophage inflammatory protein-1 alpha (MIP-1 alpha). Data regarding interleukin-3 (IL-3) and transforming growth factor-beta 1 (TGF-beta 1) were variable and inconclusive. The implications of these results to past and future clinical trials are discussed.