The induction of heat shock proteins (Hsp) is the response to a plethora of stress signals including hyperthermia, physical stress, and various disease states. Although changes in Hsp expression are associated with certain diseases, the question as to whether this is an adaptation to a particular pathophysiologic state or a reflection of the suboptimal cellular environment associated with the disease remains open. In this study we have investigated the effects of inflammatory mediators on the induction of Hsp 70 in human peripheral mononuclear blood cells using flow cytometry. We demonstrate that without heat shock, the levels of the inflammatory mediators are positively related to Hsp 70 production in monocytes. On the contrary, negative correlations were found between heat induced Hsp 70 production and interleukin-6 (IL-6), as well as various markers of inflammation. These observations are in agreement with the antagonistic effects between heat stress and the inflammatory mediators on the activation of Hsp promoter.