Objectives : This study aimed to compare the anti-diabetic efficacy of Lycii Radicis Cortex (Lycium chinense Mill.) and Corni Fructus (Cornus officinalis) on streptozotocin (STZ)-induced diabetes in rats. Methods : Male Sprague-Dawley rats were divided into four groups; normal, STZ-control, Lycii Radicis Cortex extract-administrated group (LRC) and Corni Fructus extract-administrated group(CF). Diabetes in rats was induced by intraperitonal injection with streptozotocin (STZ) at doses of, 30 mg/kg (body weight) for 5 days (once per a day). STZ-induced diabetic rats were orally administrated LRC and CF extract daily for 4 weeks at doses of 300 mg/kg. Fasting blood glucose, total cholesterol (TC), triglyceride (TG), blood urea nitrogen (BUN) and creatinine were measured in sera of rats. Histopathological changes of kidney, liver and lung tissues were observed by microscope after H&E staining. Results : There were no differences in body and kidney weights, food intake and water intake in LRC- and CF-administrated groups compared with STZ control group. However, glucose, TC and TG levels in serum were significantly decreased in LRC-administrated groups compared with STZ-control group. In histopathological analysis of kidney, liver and lung, both LRC- and CF-administrated groups showed the inhibition of morphological damage. Conclusions : These results suggest that LRC and CF have a biological action on STZ-induced diabetes in rats via decreasing the serum TG and TG levels and may protect the morphological changes of kidney, liver and lung.