The aim of the present study was to investigate the effect of aging and ovariectomy on various physiological parameters related to inflammation and oxidative stress. Female Wistar rats of 22 months of age, castrated and intact were used in the present study. Ovariectomized animals were treated for the same time with estrogens, phytoestrogens or saline. Two-month old intact female rats were used as young controls. Protein expression of iNOS, HO-1, BVR, IL-6, TNFa, and IL-1b were determined by Western blot analysis. Levels of NOx, LPO, TNFa, IL-1b, IL-6, IL- 10 and HO, FMO, GST activity were determined in different fractions of the liver. Levels of LPO in the liver homogenates and iNOS protein expression and NOx levels were increased in old as compared to young animals; these effects were more evident in ovariectomized animals. Pro-inflammatory cytokines were significantly increased and anti-inflammatory decreased during ageing and after ovariectomy. Treatment of the ovariectomized groups decreased NOx, LPO levels and pro-inflammatory cytokines as compared with untreated rats. Significant rise in IL-10 and reductions in iNOS, IL-6, TNFa and IL-1 b protein expressions were also found with both treatments. Estrogens showed also significantly up-regulated values of the protein expression of BVR. Ovariectomy and aging induced a significant decrease in GST and FMO activity. Estradiol was able to reverse these changes and also the activity HO and HO-1 protein expression. Oxidative stress and inflammation induced by aging are more marked in castrated than in intact females. Ovariectomy induced a significant decrease in drug-metabolizing enzymes compared to intact females. Administration of estradiol and phytoestrogens is capable of reducing LPO level and HO-1 and iNOS protein expression and increasing IL-10.