Our previous studies show that 2-methoxyestradiol, a non-estrogenic metabolite of estradiol (E2), attenuates the development and retards the progression of pulmonary hypertension (PH) in male rats, and in female rats prevents the exacerbation of PH and eliminates mortality due to ovariectomy. Recent studies suggest that 2-ethoxyestradiol (2-EE), a synthetic analog of 2-ME, is an even more potent antimitogen than 2-ME. The goals of this study were: 1) to compare the effects of E2, 2-ME and 2-EE on proliferation of human pulmonary artery endothelial (hPAEC) and smooth muscle cells (hPASMC) and lung fibroblasts (hLF); 2) to examine the effects of 2-ME, its metabolic precursor 2-hydroxyestradiol (2-HE) and 2-EE on isoproterenol (ISO)-induced cardiac hypertrophy in male rats; and 3) to investigate in male rats the effects of 2-EE (10 mug/kg/h via osmotic pump) on the development of monocrotaline (MCT; 60 mg/kg i.p.)-induced PH. E2 had biphasic effects on growth (stimulation at low and inhibition at high concentrations) in hPAEC and mild growth inhibitory effects in hPASMC and hLF (1-10 muM). In contrast, in all three pulmonary cell lines, 2-ME and 2-EE inhibited cell growth with 2-EE being ten times more potent than 2-ME. In ISO-induced cardiac hypertrophy, 2-ME, 2-HE and 2-EE similarly reduced (~-50%) left (LV) and right (RV) ventricular hypertrophy and fibrosis (hydroxyproline content). In animals with MCT-induced PH, treatment with 2-EE for 28 days significantly decreased the elevated RV peak systolic pressure and reduced RV/LV+septum weight ratio, strongly inhibited vascular remodeling (media hypertrophy and adventitia widening), markedly reduced inflammatory responses, and eliminated MCT-induced (63%) mortality. This study provides the first evidence that 2-ethoxyestradiol strongly inhibits vascular remodeling in PH and suggests that anti-proliferative agents, including synthetic analogs of estradiol metabolites may be protective in PH.