The effects of daily administration of Withania somnifera root extract (1.4 g/kg body wt.) and Bauhinia purpurea bark extract (2.5 mg/kg body wt.) for 20 days on thyroid function in female mice were investigated. While serum triiodothyronine (T3) and thyroxine (T4) concentrations were increased significantly by Bauhinia, Withania could enhance only serum T4 concentration. Both the plant extracts showed an increase in hepatic glucose-6-phosphatase (G-6-Pase) activity and antiperoxidative effects as indicated either by a decrease in hepatic lipid peroxidation (LPO) and/or by an increase in the activity of antioxidant enzyme(s). It appears that these plant extracts are capable of stimulating thyroid function in female mice.