Abstract: Objective To determine ATPase inhibitory factor 1 (IF1) expression in normal and pathological tissue of female reproductive system to better understand the physiological role of IF1 in malignancies of the female reproductive system. Methods Surgical specimens of normal tissues and primary malignant tumors were obtained during the past 2 years, including 38 normal endometrium tissues, 33 endometriosis tissues, 30 endometrial adenocarcinoma tissues, 24 uterine myoideum tissues, 30 uterine fibroid tissues, 18 normal cervical tissues, 30 cervical squamous carcinoma tissues, 11 fallopian tube tissues, 19 fallopian tube adenocarcinoma tissues, 15 ovarian tissues, 21 ovarian endometrial adenocarinoma tissues, 30 decidua tissues, and 30 villus tissues. The expressions of IF1 protein and mRNA were assessed by immunohistochemistry, Western blotting and RT-PCR. Results The expressions of IF1 were significantly increased in endometrial adenocarcinoma (P< 0.01), cervical squamous carcinoma (P<0.01), fallopian tube adenocarcinoma (P<0.01) and ovarian endometrial adenocarinoma (P<0.01) as compared with those in normal tissues. In normal endometrium, IF1 expression was significantly reduced in the secretory phase as compared with the proliferation phase (P<0.01). In patients with endometriosis, IF1 protein expression increased obviously in endometriotic tissues as compared with eutopic and normal endometrial, but the expression IF1 mRNA was similar among the 3 tissues. Conclusion IF1 expression, increases abnormally in malignant tumors of the female reproductive system and may serve as a marker for malignancies of the female reproductive system as well as a promising pharmacological target for cancer treatment.