Background: Pyogenic granuloma(PG) is a common lesion of the skin and mucous membranes. The gingival lesion developed during pregnancy termed epulis gravidarum is identical to PG. Many articles have appeared in the literature pertaining to this lesion and its putative relationship to the hormonal changes of pregnancy, Several clinical features such as association with oral contraceptive use and regression after delivery, suggest that PG may be a hormone-sensitive lesion. Objective: Our aim was to determine whether estrogen or progesterone might affect the development of PG. Methods: We performed immunohistochemical staining by using a monoclonal antibodies to estrogen receptor(ER) and progesterone receptor(PR) in 15 PG(pregnant women; 4 cases, non-pregnant women; 5 cases, and men; 6 cases). (continue...) (Korean J Dermatol 1999;37(5): 592-597)