Objective To investigate the expression of Calbindin-d28k (CaBP-d28k) in human endometrium.Methods Thirty-three samples of human normal endometrial tissues were divided into 6 groups: early proliferative stage (n =6), mid proliferative stage (n =5), late proliferative stage (n=5), early secretory stage (n=7), mid secretory stage (n=5) and late secretory stage (n=5). The expression and change of CaBP-d28k protein and gene were determined by immunohistochemistry and reverse transcription polymerase chain reaction methods.Results In endometrial samples, the expression of CaBP-d28k protein was mainly observed in the cytoplasm of luminal and glandular epithelium. In the menstrual cycle, the level of CaBP-d28k protein in the epithelium was the lowest during the early and mid proliferative stages, and was the highest during the mid secretory stage, then decreased in the late secretory stage (P＜0.05). In the stroma, the expressed type of CaBP-d28k protein was the same as in the epithelium, but was lower than that in the epithelium(P＜0. 05). The CaBP-d28k mRNA was at the lowest level in the early proliferative stage(P＜0. 05), and significantly increased in the late proliferative, and early,mid secretory stages (P＜0. 05).Conclusion Both CaBP-d28k protein and gene were expressed in human endometrium,and their expression had cyclic changes.