The effects of Aegle marmelos (Rutaceae) leaf, Emblica officinalis (Euphorbiaceae) fruit and Ocimum sanctum.(Labiateae) leaf extracts were studied in L-thyroxine (0.5 mg/kg) induced hyperthyroidic mice.Separately combined effects of these three plant extracts and of a commonly used antithyroidicdrug, Propyl thiouracil (PTU) were investigated for comparison. Serum concentration ofthyroxine (T4), triiodothyronine (T3), glucose and the activity of hepatic Glucose 6-Phosphatase(G-6-Pase) were considered as main parameters. Hepatic lipid peroxidation (LPO), superoxidedismutase (SOD) and Catalase (CAT) activities were also studied to reveal the toxic effect of theplant extracts, if any. While exogenous T4 enhanced serum concentration of T4, T3, glucose and theactivity of hepatic G-6-Pase, a simultaneous administration of either A. marmelos leaf (1.0 mg/kg),E. officinalis fruit( 30 mg/kg) and O. sanctum leaf (50 mg/kg) extracts, to hyperthyroidic animalsdecreased all these parameters. However, the effects were more pronounced, as nearly normalthyroid function and serum glucose concentration were exhibited when all three plant extractswere administered together. A decrease in LPO and a concomitant increase in SOD and the CATactivities indicated the safe and antiperoxidative nature of the plant extracts, administered eitheralone or in combination. Our findings reveal that the three test plant materials exhibit synergisticeffects without any hepatotoxicity, suggesting their potential use in the amelioration ofhyperthyroidism and/ or hyperglycaemia.