Several methods have been developed to evaluate and quantify the effects of Endocrine disruptor chemicals (EDC). Nevertheless, most of these methods are time-consuming or not enough sensitive to detect EDC at the environmental range. To link the biological effect of tested EDC to natural protein secretion, we have developed a new screening method based on the secretion of the cytokine CXCL12 (or SDF-1, Stroma-cell Derived Factor 1), which plays a capital role in cell survival and migration. We have demonstrated that CXCL12 secretion is regulated by estrogenic compounds in a dose-dependent way in ER-positive breast cancer cell lines (MCF-7 and T47D). By combining cell culture and ELISA test, we used this up-regulation of CXCL12 secretion to test several major environmental contaminants. Our results showed that 17β-estradiol (from 10(-11) M), 17α-ethynylestradiol (from 10(-12) M), genistein (from 10(-8) M) and bisphenol A (from 10(-6) M) dose-regulate CXCL12 secretion in T47D. In contrast, antiestrogens, raloxifen and 4-hydroxytamoxifen, had no effect on the CXCL12 secretion, but were able to inhibit E2 effect. Moreover, we used cell proliferation assays to evaluate the effect of these different compounds on the growth of T47D cells. We found strong correlation (P = 0.7) between proliferation and CXCL12 secretion. However CXCL12 secretion was as sensitive as cell proliferation assays but appeared more rapid. Thus, this bioassay named CXCL-test (for Checking Xeno-estrogen activity by CXCL12 secretion in breast cancer cell Lines) constitutes a fast and sensitive method for the detection of estrogenic compounds allowing in 14 h to achieve a detection limit of 10(-11) M of E2 (2.7 ng/L).