Leukocyte populations change profoundly in the human endometrium during the menstrual cycle. However the predominant cell, the uterine natural killer (uNK) cell does not contain steroid receptors. From gene array analysis we identified a transcript encoding chemokine (C-X-C motif) ligand 14 (CXCL14) which is markedly up-regulated in the secretory phase of the cycle. We confirm this data by northern blotting and quantitative PCR. Using in situ hybridization we localized CXCL14 mRNA to the glandular epithelial cells where it was detected only in the secretory phase of the cycle. Candidate progesterone response elements were identified at positions -2028/-2007 and -722/-697 (PRE1 and PRE2, respectively) relative to the translation start site. These were functionally tested using luciferase reporter deletion constructs, electrophoretic mobility shift assays and site-directed mutagenesis. The deletion/mutation of these sites reduced progesterone induction by 40 and 20%, respectively. Finally, we demonstrated that recombinant CXCL14 stimulated uNK cell chemotaxis in vitro. We therefore conclude that CXCL14 is likely to be regulated by progesterone in human endometrium and that it may exert a chemoattractive effect on uNK cells and in part be responsible for their clustering around the epithelial glands.