Implantation of the blastocyst and early development of the placenta are crucial for successful fetal growth and development. These processes are promoted by the integration of a complex network of signalling molecules mediating cell-to-cell / cell-to-extracellular matrix communication. Accum-ulating evidence suggests that Wnt signalling pathways play an important role in implantation and placentation. To date, there have been no studies looking specifically at Wnt signalling cross-talk between trophoblast (fetal) and decidua (maternal) cells in vitro. We have utilised two powerful techniques to investigate Wnt signalling in trophoblast and endometrial cell crosstalk. Term placental tissues were collected and decidua and trophoblast cells were extracted and purified. These two cell populations were cultured either separately or in a co-culture setting using Transwell inserts for 3 days, mRNA was extracted (n=3) and conditioned media harvested. Expression analysis of Wnt components using a Wnt PCR array (Qiagen) was performed on cDNA from pure trophoblasts, decidual cells and mixed co-cultured cells. Expression data were normalised to 3-5 housekeeping genes and the effects of cell-type and co-culture were assessed. The majority of the 84 Wnt-related genes on the array were detectable in both cell types, with Wnt5A/5B, β-catenin, dishevelled homolog 1 and glycogen synthase kinase 3b being highly expressed in both trophoblast and decidua. Relative expression of secreted Wnt antagonists dikkopf-1 (Dkk1) and soluble frizzled-related protein 4 (sFRP4) was higher in decidua, while sFRP1 expression was higher in trophoblast. The majority of genes were not differentially expressed in co-culture; however, expression of the secreted Wnt inhibitors sFRP4 and WIF-1 (Wnt inhibitor factor-1) was down-regulated in trophoblast and decidua co-culture, respectively. Release of DKK-1 into the media from decidual and trophoblast cells in co-culture was reduced by 40-60%. Our data show that the differences in Wnt signalling factor expression between trophoblast and decidua mostly reside in secreted Wnt antagonists, possibly reflecting paracrine regulation of Wnt signalling involved in trophoblast-decidual communication necessary for successful implantation.