Aim To study the effect of estrogen(E)or estro-gen combined with progestogen(P)on atherogenesis and the mechanism in ovariectomized rabbits.Methods 40 ovarictomized rabbits were randomized into low E,low EP,high E,high EP and control groups.Each group was fed high cholesterol diet for 14 weeks.Group low E,low EP,high E,high EP were replaced different dose of estrogen or estrogen combined with progestogen.Before the experiment,at the end of the fourth or fourteenth week,the serum lipid,MDA and SOD were determined.At the end of the experiment,the plasma 6-keto-PGF1αTXB2 and ox-LDL levels were assayed.After killing the ani-mals,pathomorphological examination was carried out.Results Compared with the control group,the serum levels of total cholesterol(TC),triglyceride (TG),MDA and plasma ox-LDL,TXB2 concentra-tions were significantly lower(P<0.05~0.01)in the groups of the hormone replacement.While the plas-ma 6-Keto-PGF1αconcentrations were signicantly high-er(P<0.05).The plaque areas percent of the whole aortic intima surface areas in the therapy groups re duced by 57.8% averagely(P<0.01).Conclusion Estrogen could inhibit the aortic atherogenesis of the rabbits,its methanisms might be associated with serum lipid-lowing,inhibition of the lipidoxidation and regulation of the prostaglandin metabolism.Progestogen had no anti-atherosclerotic effect on ovariectomized rabbits.