Abstract: Objective To determine the effects of hypobaric hypoxia pretreatment on surgically induced endometriosis in rats. Methods Six rats were randomized into 2 groups and exposed to hypoxia (8% O2) and normoxia (21% O2) for 8 h. The uterine endometrium was intraperitoneally implanted into estrogen-treated ovariectomized Lewis rat, and the growth and quality of the implants were measured. The changes in apoptosis, protein and gene expressions in the serum, abdominis effusion fluids and implants were tested by ELISA, immunohistochemical staining, TUNNEL assay, Western blotting and RT-PCR. Results The volume of the implants in the hypoxic pretreatment group was significantly increased compared with the normoxia group. High expressions of Ki67, CD31, VEGF, and HIF-1α and lowered cell apoptosis were found in the hypoxia-pretreated implants compared with the normoxic group. VEGF level in the serum and peritoneal fluid were increased in hypoxia-pretreated group, but TNFα level was comparable between the 2 groups. Conclusion Hypoxia play an important role in the occurrence and progression of endometriosis by increasing cell proliferation and angiogenesis and decreasing cell apoptosis in the implants in the rat model.