Among the newly synthesized 1, 1, 2, 2-tetraallryl-l, 2-diphenylethanes, 1, 1, 2, 2-tetramethyl- 1, 2-bis (4'-hydroxyphenyl) ethane (23) and 1, 1, 2, 2-tetramethyl-1, 2-bis (3'-hydroxyphenyl) ethane (26) were the most active compounds regarding estradiol receptor affinity, exhibiting K, values of 0.73 X los and 0.67 X lo8 Ml, respectively. In vivo, 23 and 26 showed only very small uterotrophic activity in the mouse. They strongly inhibited (73%) the estrone- ...