Evidence is presented which indicates the lack of effect of delta-9-tetrahydrocannabinol or cannabis resin on tritiated estradiol-17beta binding to uterine cytosol receptor. The cannabinoids which demasculinize when given in vivo had no estrogneic properties as assessed by receptor studies on 2 different rodent species. None of the major metabolites seems to have free hydroxyl or phenolic groups at both extremities of the molecule. It is concluded that it is very unlikely that the demasculinizing and/or feminizing effects of cannabis are due to simple estrogenlike action.