Since ancient times, extracts of plants have been used for women's health to prevent menopausal symptoms. The symptoms of menopause have been attributed to a reduction in the amount of estrogen produced by the ovaries. In this study the estrogenic activity of a commercial standardized extract of the roots of Angelica sinensis, used to relieve climacteric symptoms was evaluated using in vivo tests such as the degree of cornification of vaginal epithelium, uterotrophic assays and serum LH concentration in ovariectomized rats. Furthermore, the effects on the estrous cycle in rat were investigated. The results obtained have shown that the administration of a standardized ethanol extract in ovariectomized rats exhibited a stimulation of the uterine histoarchitecture, a significant cornification in the vaginal epithelium and a reduction of serum LH concentration showing the estrogenic nature of the extract. Furthermore, the administration of the extract in intact female rats provoked a significant modification of the vaginal smear in 67% of treated rats. The estrous cycle thus modified was characterized by a prolonged estrus stage with a temporary reduction of the regular cyclicity.