The stem bark of Erythrina lysistemon, one of the traditionally used "women remedies", has been assessed for its estrogenic activity. The ethyl-acetate extract of the stem bark of E. lysistemon showed estrogenic activities in vitro either in a yeast-based estrogen receptor assay or on the estrogen-dependent stimulation of alkaline phosphatase activity in the human endometrial carcinoma cell line Ishikawa. The estrogenic activity was investigated in vivo in young ovariectomized Wistar female rats after a 7-day treatment. The estrogenicity was evaluated through the proliferative status of target sex organs such as uterus and vagina. The results obtained showed that oral administration of 200 mg/kg BW/d of E. lysistemon extract in comparison to untreated ovariectomized rats significantly increased the vaginal epithelial height by 47.23% (from 8.71+/-0.47 to 12.34+/-1.31 microm); and induced a weak increase of uterine epithelial height by 6.76% (from 5.42+/-0.52 to 5.84+/-0.91 microm). Both were not as pronounced as those elicited in the positive control of 100 microg/kg BW/d of ethinylestradiol given orally. Overall our results suggest that the extract of E. lysistemon contains secondary metabolites endowed with estrogenic activity.