Sanchinoside C1 (ginsenoside Rg1), one of the major effective components of Panax notoginseng, was reported to be effective in lowering glucose-induced hyperglycemia and synergizing the action of insulin in normal animals. The present study was aimed at investigating its effects on diabetic animals and comparing them with that of insulin. The results showed that sanchinoside C1 was able to lower plasma glucose level in alloxan-diabetic mice. The action was strengthened with repeated administration and tended to be dose-dependent; its effect lasted for more than four hours and no synergism or antagonism between sanchinoside C1 and insulin was observed. A single dose of sanchinoside C1 neither elevated plasma insulin level nor lowered hepatic cAMP level in alloxan-diabetic mice; while the uptake of [3H] glucose by isolated rat hepatocytes, oxidation of glucose and sodium succinate in liver homogenate and synthesis of liver glycogen in normal mice were increased.