Abstract: In experiments carried out in mice,hamsters,guinea pigs and rabbits bothdihvdroartemisinin and artesunate showed contragestational effect.In mice and rabbits they causedembryo absorption whereas in hamsters and guinea pigs they induced abortion. The contragestationalED₅₀ of dihydroartemisinin given sc on d 7 of pregnancy in mice and d 5 of pregnancy in hamsters were32.8(27.7～38.9)mg.kg^-1 and 6.1(5.6～6.7)mg·kg^-1 respectively.The ED₅₀ of this drug givenim on d 18 of pregnancy in guinea pigs was 18.3(13.9～24.2) mg·kg^-1. Dihydroartemisinin alsoshowed mid-pregnancy terminating effect in hamsters. The contragestational ED50 of artesunate givensc on d 5 of pregnancy in hamsters and the ED50 of sodium artesunate given sc on d 5～8 of pregnancyin hamsters were 12.2(10.3～14.4)mg.kg^-1 and 1.0(0.9～1.2)mg·kg^-1 daily respectively。Results of light microscopic examination revealed that dihydroartemisinin was selectively toxic toembrvo sac,At dose levels sufficient to induce embryo sac necrosis,dihydroartemisinin did not injurethe uterus and ovarv of the maternal animals.On the ground of the foregoing observations we considerthat dihvdroartemisinin,artesunate and their analogous drugs should not be used to treat malaria inpregnant women and there is the possibility to exploit intent ional abortion agents from artemisininderivatives.