AbstractThe hexane extract ofFerula jaeschkeanawas studied for its effects on the oestrogenic rhythm following a single administration to immature rats. A 25 mg/kg single oral dose significantly increased the uterine wet weight and caused premature opening of the vagina and induced vaginal cornification. A uterotrophic peak was attained 2 days after administration and thereafter declined gradually. At 10 days, values became almost normal. A significant amount of glycogen was estimated in the uterus during the first 5 days after administration and thereafter decreased significantly. Histoarchitecture of the uterus showed a stimulated endometrium which continued for 6–8 days only. The oestrogenic rhythm induced by the hexane extract was compared with that following diethylstilbesterol administratio