Gynostemma pentaphyllum is a traditional Chinese medicine used for a variety of conditions, including elevated cholesterol. We have examined the pharmacological anti-hyperlipidemic and hypoglycemic effectiveness of Gynostemma pentaphyllum in the obese Zucker fatty diabetic rat model. After treatment for 4 days Gynostemma pentaphyllum 250 mg/kg reduced triglyceride (33%), total cholesterol, (13%) and low density lipoprotein cholesterol levels (33%). These effects were dose-dependent and maintained for at least 5 weeks. Chronic treatment for 3-5 weeks also reduced post-prandial hypertriglyceridemia induced by olive oil 10 mg/kg in the Zucker fatty rats but had no significant effect in lowering sucrose-induced hyperglycemia in Sprague-Dawley rats. A novel regulation by Gynostemma of glucose levels was also observed in the Zucker fatty rat model. In a glucose tolerance test in obese and lean Zucker rats pretreatment with Gynostemma pentaphyllum 250 mg/kg demonstrated glucose levels were significantly less 2 hours post challenge (20%) in the Gynostemma pentaphyllum obese rats compared to the control group. Gynostemma pentaphyllum did not significantly reduce glucose levels at 120 min in the lean strain, in contrast to the 20% decrease seen in the obese rat. In vitro, Gynostemma pentaphyllum inhibited alpha-glucosidase activity (50% inhibition at 42.8), which compared to acarbose (50% at 53.9 microg/mL). The improvement in glucose tolerance at 120 min by Gynostemma pentaphyllum in obese Zucker fatty rats but not lean rats suggests that it may improve insulin receptor sensitivity and together with the significant reduction of hypertriglyceridemia, cholesterol and low density lipoprotein cholesterol suggests that Gynostemma should be examined further by oral hypoglycemic/anti-hyperlipidemic therapy.