This invention provides a 1,1,2-triaryl-1-butene derivative of the formula ##STR1## wherein R.sub.1 and R.sub.2 each represent a lower alkyl group, one of R.sub.3 and R.sub.4 is a lower alkyl group and the other is a group of the formula ##STR2## (in which R.sub.5 is a hydrogen atom, a lower alkyl group, a lower alkoxy group, a halogen atom or --OPO(OH).sub.2 group); or a pharmacologically acceptable salt thereof, its preparation and agents containing the derivative for treating mammary cancer and anovulatory infertility.