Soluble cytokine receptors are more general phenomena and play a wider physiological role in the regulation of the immune system than previously recognized. Soluble IL-6 receptor (IL-6sR) and soluble TNF receptors (sTNF-Rs) might play a regulatory role in a variety of normal and abnormal reactions mediated by IL-6 and TNF-alpha. The release of IL-6sR and sTNF-Rs by polymorphonuclear cells (PMNs) of breast cancer patients in vitro was measured. The results obtained were compared to the secretion of these soluble receptors by whole blood cells (WBC). We found that PMNs of patients examined secreted the concentrations of IL-6sR as in healthy subjects. Simultaneously, significantly higher values of sTNF-RI and sTNF-RII released by PMNs of patients were measured in comparison with the values of the control group. The mean concentrations of IL-6sR and sTNF-Rs secreted by WBC of control and cancer groups were higher than those released by PMNs. Altered secretion of sTNF-Rs and no altered secretion of IL-6sR by PMNs of breast cancer patients may have various implications for response to malignancy.