N-Butanol fraction of aerial parts of ACHYRANTHES ASPERA Linn. prevented pregnancy in adult female rats when administered orally at 75 mg/kg dose on days 1-5 POST-COITUM, but was ineffective in hamsters upto 300 mg/kg dose. In ovariectomized immature female rats, the extract exhibited potent estrogenic activity at the contraceptive dose but was devoid of any antiestrogenic activity. 100% uterine weight gain was achieved at 1/15th of the contraceptive dose. Significant uterotrophic effect was discerned even at 1/20th of the contraceptive dose. Taking 100% increase in uterine weight as the parameter, estrogenic activity of the extract was found to be 1/2750 that of ethynylestradiol.