This study examined the impact of luteinized unruptured follicle (LUF) on endometrial receptivity.The menstrual cycle of 17 LUF patients (LUF group) and 13 ovulatory women (control group) was monitored by measuring LH level in urine and by ultrasonic examination.An endometrial biopsy at the sixth to tenth day after LH surge was taken in all the patients.The expressions of endo-metrial ER,PR and integrin avβ3 were immunohistochemically determined.At the same time,the serum levels of E2 and P were detected by chemiluminescence.The results exhibited that (1) The mean serum P level in LUF group (7.32±2.56 ng/mL) was significantly lower than that in control group (11.17±3.17 ng/mL) (P＜0.01).But there was no significant difference in the mean serum E2 levels between LUF group (179.35±81.60 pg/mL) and the control group (198.58±75.23 pg/mL) (P＞0.05); (2) The mean expression intensities of ER,PR in endometrium of LUF group (183.86±2.43,167.94±3.04) were significantly higher than those in control group (109.35±6.31,105.98±4.07)(P＜0.01); (3) The mean expression intensities of integrin αvβ3 in endomtrium of LUF patients (114.90±11.38) were significantly lower than those in control group (191.34±1.82) (P＜0.01); (4)The change profile of integrin αvβ3 expression in the endometrium of LUF patients was in positive relation with serum P level (r=0.77,P＜0.01),but bore no significant relationship with serum E2 level (r=0.01,P＞0.05).It was concluded that the depression of serum P levels in LUF patients was closely related to the failure of the down-regulation of ER and PR,and the low expressions of integrin αvβ3 also suggested that the delayed implantation and the impaired endometrial receptivity had impact on embryonic implantation.