Estrogen affects proliferation and migration of different skin components, thus influencing wound healing processes. The human keratinocyte cell line NCTC 2544 has been used to examine the effects of estrogen, dissect its mechanism of action and characterize receptor subtypes involved. Western blot and immunocytochemical analyses confirmed the expression of estrogen receptors (ERs) a and b, with prevalence in the nuclear and extranuclear compartment, for ERa and ERb respectively. Treatment with 10 nM 17bestradiol (17b-E2) and the ERa and ERb selective agonists, 1, 3, 5-tris (4-hydroxyphenyl)-4-propyl-1H-pyrazole (PPT; 100 nM), and diarylpropionitrile (DPN; 1 nM) produced a slight but significant increase in cell proliferation, as by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide and bromodeoxyuridine incorporation assays, only after a longterm treatment (96 h). Analysis of cell migration by a scratch wound assay showed that 17b-E2 (10 nM) accelerated migration between 5 and 24h after scratching, an effect confirmed by the transwell migration assay. PPT and DPN elicited similar effects. Pre-treatment with the mitogenactivated protein kinase inhibitor, U0126 (1 mM), abolished the ability of 17b-E2 and DPN, but not of PPT, to accelerate wound closure. TGF-b1 (10ng/ml) produced a similar positive effect on wound closure and the TGF-b1 receptor antagonist, SB431542 (10 mM), reduced the ability of 17b-E2 and PPT to accelerate cell migration, but did not modify DPN effect. It is suggested that estrogen positively affects in vitro wound healing by stimulating cell proliferation after long-term exposure but mainly by accelerating cell migration within a few hours from treatment. Selective activation of ERb may result in favorable stimulation of wound healing without any increase of transforming growth factor-b1 production.