The antihyperglycemic effect of the Antidiabetis herbal preparation ((Myrtilli folium (Vaccinium myrtillus L.), Taraxaci radix (Taraxacum officinale Web.), Cichorii radix (Cichorium intybus L.), Juniperi fructus (Juniperus communis L.), Centaurii herba (Centaurium umbellatum Gilib.), Phaseoli pericarpium (Phaseolus vulgaris), Millefollii herba (Achillea millefolium L.), Morii folium (Morus nigra L.), Valeriane radix (Valleriana officinalis L.), Urticae herba et radix (Urtica dioica L.)), patent No. P-9801091 Zagreb, Croatia was investigated. Two extracts were prepared: ethanol extract (extract 1), and ethanol extract from which ethanol was evaporated on a rotatory evaporator at a temperature of 45 degrees C (extract 2). Extract 1 and extract 2 were administered (in experiment 1) to alloxan-induced non-obese diabetic (NOD) mice in the same dose of 20 mg/kg. Blood glucose was determined before, and 10, 30, 60 and 120 min after the preparation administration. Extract 1 and extract 2 decreased the level of blood glucose by 10 and 20%, respectively, of the initial value (at 0 min, mean = 22.6 +/- 8.3 mmol/l). Serum levels of glucose and fructosamine were determined in NOD mice, NOD mice administered extract 2 in a dose of 20 mg/kg of extract 2, and NOD mice administered acarbose in a dose of 25 mg/100 g chow, in order to verify the hypoglycemic action of extract 2 (in experiment 2). Extract 2 and acarbose were admixed to the chow. The duration of treatment was 7 days. Significantly lower glucose (P < 0.05) and fructosamine (P < 0.001) levels were recorded in extract 2 treated NOD mice as compared with NOD mice. Study results showed extract 2 to significantly decrease the level of glucose and fructosamine in alloxan induced NOD mice. Our future studies will be focused on the search of active principles of the extracts.