Early molecular interaction between embryo and mother, involving chemoattractants, especially chemokine CXC-motif ligand 1 (CXCL1)(2), determines the pregnancy outcome. So far nothing is known about the signalling cascades of CXCL1 expression in human decidua. The aim of the study was to identify signalling cascades mediating the CXCL1 expression in human decidua incubated with IL-1ß as a major secretion product of the embryo. Therefore, decidualised endometrial stromal cells were incubated with IL-1ß in a concentration- and time-dependent manner. The specificity of the IL-1ß induced CXCL1 expression was verified by application of the IL-1 receptor antagonist, which opposed the binding of IL-1ß to its receptor, leading to a dose dependent diminished to complete CXCL1 elimination. IL-1ß signalling was investigated using inhibitors for MAPK, STAT3 and JNKinase cascades. The CXCL1 secretion of decidualised endometrial cells was measured by ELISA. The MAPK signalling cascade was explored by western blot analysis of ERK and NFκB p65(3) as well as phospho ERK and pp65 activation by IL-1ß in detail. A statistical significant increase in CXCL1 mRNA- and protein-expression after incubation with 0.1ng/ml IL-1ß after 48h was detected. CXCL1 protein secretion could be completely prevented by IL-1 receptor antagonist treatment. Only inhibition of the MAPKinase pathway resulted in a statistically significant decrease of CXCL1 protein secretion. Initiation of the MAPK pathway depicted by phospho ERK activation started as early as 2min after coincubation of decidualised endometrial stromal cells with IL-1ß. Activation of NFκB p65 could be measured within 15min of IL-1ß incubation in decidualised endometrial stromal cells. CXCL1 is a target for the embryos' secretion product IL-1ß in decidualised endometrial stromal cells during the peri-implantation period. IL-1ß's rapid effect on CXCL1 synthesis is uniquely mediated via the MAPK-signalling cascade and the activation of CXCL1s' transcription factor NFκB p65.