The most common strategy for drugs development from plant resources is careful observation of the use of natural resources in folk medicine. In Brazil, medicinal plants are widely used according to folk medicine. Objectives:In the present study, we evaluate the effect of Trema micrantha ethanolic crude extract (ECE) in different concentration about serum glucose, since this plant is used in south Brazilian folk medicine to reduce glucose levels. Studies have shown that terpenoids isolated from medicinal plants present antidiabetic activity (LI, 2004) Methods: Male albino Wistar rats (200 – 250g) were used in the experiment. Overnight fasted animals (normal animals) were divided into two groups (n=6): ECE (250, 500, 1.000 mg/kg v.o.); control (vehicle v.o.). Blood was collected by ocular puncture 1, 2 and 3 hours after treatments and glucose levels was determined. For oral glucose tolerance test fasted rats were divided into three groups (n=6): hyperglycemic rats (glucose 4 g/kg, v.o), ECE (glucose plus 250, 500, 1.000 mg/kg v.o.); control (vehicle v.o.). Blood was collected by ocular puncture 30, 60, 90 and 180 minutes after treatments and GL levels were determined. Diabetes was induced by a single intraperitoneal injection of 200 mg/kg of alloxan monohydrate (dissolved just before use in water). Animals whose development of hyperglycemia (serum glucose levels > 300 mg/dL) were allocated into two groups (n=6): ECE (250, 500, 1.000 mg/kg v.o.); control (vehicle v.o.). Blood was collected by ocular puncture 1, 2 and 3 hours after treatments and glucose levels were determined. Results: Neither tested dose has shown significant lowering of blood glucose when compared to the “zero time” of each respective dose for normal rats. None tested concentration of ECE prevented significantly the increase in blood glucose levels after glucose administration. ECE showed significant reduction in the blood glucose levels for 250 mg/kg in 1h (56%; P<0.001), 2h (52%; P<0. 01) and 3 h (55%; P< 0.001), and 1.000 mg/kg in 1h (36%; P<0.001), 2h (32%; P<0. 01) and 3 h (47%; P< 0.001) for diabetics rats. Conclusion: In accord with folk use T. micrantha was showed hypoglycemic activity and once this medicinal plant has terpenoids in its constitution (FRIMMEL, et al, 2000), its hipoglycemyc effect could be related to these metabolites.