Treatment with tamoxifen at the dose of 4mg·kg-1 on day 7 - 9 of gestation had significant effect on terminating early pregnancy in rat. Tamoxifen combined with a non-effective dose of 1. 0mg · kg-1 mifepristone was shown to have a synergistic effect on terminating early pregnancy. Tamoxifen combined with an effective dose of 4. 0mg · kg-1 mifepristone was shown to have significantly decreased effect on terminating early pregnancy. 1. 0mg · kg-1 mifepristone + 4. 0mg · kg-1 tamox-ifen on day 7-9 of gestatio...