Nasopharyngeal angiofibroma is an uncommon tumor arising in adolescent males, suggesting that the tumor may be hormonally responsive. Previous studies have found androgen receptor (AR) expression but variable expression of estrogen receptor (ER). The recently described ss receptor for estrogen has not been analyzed in angiofibroma. We analyzed 13 cases of nasal angiofibroma by immunohistochemical analysis for the presence of ARs, progesterone receptors (PR), and ER-a and ER-ss. All 13 cases were positive for ER-ss, in stromal pericytic and endothelial cells, and 12 of 13 stained strongly. Five cases were positive for AR in stromal cells, most staining weakly, and with no staining in endothelial or pericytic cells. None of the cases displayed staining for ER-a or PR. The findings confirm that nasopharyngeal angiofibromas express ER and suggest that new modulators of ER-ss activity may provide an alternative therapy for these lesions.