The present study was undertaken to evaluate the endometrial secretion and synthesis of proteins in hamsters that were subjected to ovarian stimulation with or without GnRH agonist (Leuprolide Acetate, LA). The results of protein resolution revealed that the molecular weight of the proteins increased from 31D to 66D, while the intensities of photographed protein bands in the hamsters treated with LA and pregnant mare’s serum gonadotropin (PMSG) were less than that in those treated with PMSG alone. The amounts of low and medium weights (31kD and 45kD) proteins newly synthesized in LA+PMSG group and saline group (control) were significantly higher than that in PMSG group. The synthesized and secreted proteins in groups LA and control were similar. The data suggested that a physiologic endometrial protein secretory and synthetic change with GnRH agonist regarcded as a possible cause of the higher pregnancy rate in in vitro fertilization. The degree of endometrial secretion and synthesis varied considerably with the type of ovarian stimulation used. The present study was undertaken to evaluate the endometrial secretion and synthesis of proteins in hamsters that were subjected to ovarian stimulation with or without GnRH agonist (Leuprolide Acetate, LA). The results of protein resolution revealed that the molecular weight of the proteins increased from 31D to 66D, while the intensities of photographed protein bands in the hamsters treated with LA and pregnant mare’s serum gonadotropin (PMSG) were less than that in those treated with PMSG alone. The amounts of low and medium weights (31kD and 45kD) The synthesized and secreted proteins in groups LA and control were similar. The data suggested that a physiologic endometrial protein secretory and synthetic change with GnRH agonist regarcded as a possible cause of the higher pregnancy rate in in vitro fertilization. The degree of endometrial secretion and synthesis v aried considerably with the type of ovarian stimulation used.