Successful implantation necessitates modulation of the uterine environment by the embryo for a specific period of time during the menstrual cycle. Infusion of chorionic gonadotropin (CG) into the oviducts of baboons to mimic embryo transit induces a myriad of morphological, biochemical and molecular changes in the endometrium. Endometrial epithelial cells from both baboons and humans when stimulated by CG in vitro, activates a cAMP independent mitogen activated protein kinase (MAPK) pathway leading to prostaglandin E₂ (PGE₂) synthesis. This study shows that in the human endometrial cell line, HES, CG, acting via its G-protein coupled receptor, phosphorylates protein kinase B (Akt), c-Raf and the extracellular regulatory kinase, ERK1/2 in a phosphatidylinositol 3-kinase (PI3K) dependent manner. Further, ERK1/2 phosphorylation is independent of the signaling paradigms of G_s, G_i and epidermal growth factor receptor (EGFR) transactivation, typical of gonadal cells, indicating an alternative signaling pattern in the endometrium. Following phosphorylation by CG, ERK1/2 translocates to the nucleus in a time dependent manner. Downstream of ERK1/2, CG activates the nuclear transcription factor, Elk1, also in a PI3K-MAPK dependent manner. Lastly, we show that in HES cells, this pathway regulates the expression of the microsomal enzyme prostaglandin E synthase (mPTGES), a terminal prostanoid synthase responsible for PGE₂ synthesis. CG regulates the mPTGES promoter and also induces mPTGES synthesis in HES cells via the PI3K-ERK1/2 pathway. We suggest that this alternative PI3K-ERK-Elk pathway activated by CG regulates prostaglandin production by the endometrial epithelium and serves as an early trigger to prepare the endometrium for implantation.