Abstract: Objective To investigate the effects of medroxyprogesterone acetate (MPA) on angiogenesis and growth of transplanted human ovarian cancer cells in nude mice. Methods Ovarian cancer cell line COC Ⅰ derived from human ovarian serous adenocarcinoma was transplanted into 30 nude mice, which were then randomized equally into 3 groups consisting of two treatment groups (in which MPA was administered at 60 and 120 mg/kg, respectively, twice a week for 4 weeks) and a control group. Six weeks later, the body mass of the nude mice was recorded and the morphology of tumor cells observed by electron microscope. The microvascular density (MVD) was examined by immunohistochemical staining with anti-human factor Ⅷ antibody. Results Compared with the control group, the growth inhibitory rate in the two treatment groups were 23.76% and 43.80%, respectively, corresponding to the doses of 60 and 120 mg/kg. MVD of 60 mg/kg MPA group (3.64±0.02) and 120 mg/kg MPA group (2.11±0.12) was lower than that of the control group (5.14±0.74) (P<0.05 and P<0.01, respectively), and there was also significant difference between the two treatment groups (P<0.01). The morphological changes including compaction and margination of the nuclear chromatin, apoptotic bodies, and cell necrosis were significantly increased in the two treatment groups. Conclusions MPA can inhibit the angiogenesis and growth of transplanted human ovarian cancer cells in nude mice in a dose-dependent manner, and its anticancer effect may involve induction of cell apoptosis as the result of its effect against angiogenesis.