Estrogen deficiency associated endothelial dysfunction contributes for the increased cardiovascular incidence in postmenopausal women. Because of the many complications presented by estrogen therapy, alternative therapies have emerged. The SERMs are a class of synthetic compounds that act as antagonists or agonists of the estrogen receptors. Tamoxifen (TAM) is the most widely used anti-estrogen for the management of breast cancer. Raloxifene (RAL) is used for the treatment and prevention of post-menopausal osteoporosis. This study evaluated the influence of RAL, TAM and 17-β estradiol (E) treatment on mesenteric bed (MB) vascular reactivity in rats with E deficiency. The investigation was conducted in accordance with the biomedical research guidelines for the care and use of laboratory animals, and it were approved by Ethics Committee (n°012/2008). All the surgical experiments were carried out under anesthesia (Ketamine70mg/kg+xylazine10mg/kg,i.p). Female rats were studied (n=6/group): control (SHAM); ovariectomized (OVX), OVX treated with E (0.5µg/Kg/day), RAL (2mg/Kg/day) or TAM (1mg/Kg/day), 21 days after bilateral ovariectomy. On day 35, the MB was isolated, perfused and constricted with noradrenaline. Dose response curves of ACh were obtained in absence or presence of L-NAME (NOS inhibitor) or aminoguanidine (AG iNOS inhibitor). Inducible NOS (iNOS), endothelial NOS (eNOS) and NADP(H) oxidase protein expression by western blot were analyzed. The data are reported as means±SEM, compared by ANOVA. The vasodilatation obtained in the OVX was lower compared to the SHAM Emax81±3 vs 60±3 %relaxation P<0.05. In the presence of L-NAME EmaxSHAM 31±3; OVX 21±2; E 34±9; RAL 16±2; TAM 19±4 %relaxation, decreased in all groups. In the presence of AG EmaxSHAM 76±3 vs OVX 36±3 %relaxation P<0.05; the concentration-response curve for Ach was reduced further in the OVX group and the other groups did not change when compared with non-blocking EmaxE 79±4; RAL 80±8; TAM 63±3. The levels of iNOS and NADP(H) oxidase (NOX2) protein expression in MB were elevated in OVX iNOS: SHAM 0.84±0.05; OVX 0.99±0.04 P<0.05 and NOX2: SHAM 0.76±0.10; OVX 1.12±0.13 P<0.05, while levels of eNOS were reduced in OVX when compared to SHAM eNOS: SHAM 1.07±0.10; OVX 0.71±0.10 P<0.01. All treatments were able to restore the protein expression values to those similar to control group iNOS: E 0.81±0.05; RAL 0.65±0.07; TAM 0.69±0.06; eNOS E 1.13±0.08; RAL 0.91±0.02; TAM 0.99±0.08 and NOX2 E 0.80±0.07; RAL 0.58±0.04; TAM 0.68±0.02. The treatments were able to normalize the impaired vasorelaxation of estrogen-deficient rats, indicating that despite the estrogen and SERMs present structural differences in treatment efficacy was similar to reduce a possible inflammatory and improve vascular reactivity in rats with endothelial dysfunction.