The therapeutic anti-diabetic effect of SMK001, a poly herbal formula was evaluated in the streptozotocin (STZ; 60 mg/kg, single intraperitoneal injection) induced diabetic rats. For therapeutic study, test articles were orally dosed once a day from 21 d after STZ-dosing at 100, 200 and 500 mg/kg/5 ml dosage levels for 4 weeks. The body weight changes, blood and urine glucose level changes were monitored with changes on the pancreas weight, and after sacrifice, the histopathological changes of pancreas and the changes of insulin- and glucagon-producing cells were also observed by immunohistochemistry. The results were compared to that of glibenclamide 5 mg/kg-dosing group. Significantly (p<0.01 or p<0.05) decrease of body weight, blood and urine glucose levels were detected in STZ-induced diabetic animals with disruption and disappearance of pancreatic islets. In addition, significantly (p<0.01) increase of glucagon- and decrease of insulin-producing cells were detected in STZ induced diabetic rats. However, these diabetic changes were significantly (p<0.01 or p<0.05) and dose dependently decreased in SMK001-dosing groups, and SMK001 100 mg/kg showed more favorable effects compared to that of glibenclamide 5 mg/kg. Based on these results, it is considered that SMK001 has favorable effect to inhibit the changes on the blood and urine glucose levels, body weight and the histopathological changes of pancreas in STZ induce diabetes.