The aim of this study was to simultaneously determine IL-6, M-CSF and IAP levels in 61 serum samples of previously untreated ovarian cancer patients. A direct correlation between IL-6 and M-CSF has been found in our patient population (r = +0.41, p = 0.013), while IAP serum levels failed to correlate with M-CSF (r = +0.15, p = 0. 24) and IL-6 (r = +0.17, p = 0.18) levels. Since IL-6 and M-CSF have been demonstrated to be both induced in response to the same agents, it is conceivable that a mechanism of coregulation in the production of these cytokines by tumor cells and macrophages might occur. The direct correlation between IL-6 and M-CSF also suggests that tumor-derived cytokines can potentially lead to a self-maintaining cytokine network by recruiting cytokine-producing host cells and by perpetuating cytokine production.