To compare the anti-diabetic effects of dietary ginger and garlic, 5-week-old male Sprague-Dawley rats were fed a high-fat (HF) diet (22% fat) for 2 weeks and then randomly divided into six groups of eight animals: Normal Control (NC), Diabetic Control (DBC), Ginger Low (GNL), Ginger High (GNH), Garlic Low (GRL), and Garlic High (GRH) groups. "Low" and "High" indicate addition of 0.5% and 2.0% freeze-dried ginger or garlic powder in their respective diets. Diabetes was induced by an intraperitoneal injection of streptozotocin (40 mg/kg of body weight) in all groups except the NC group. After 4 weeks of feeding of experimental diets, food intake was significantly (P < .05) higher in the GRL group compared to the GRH group. Serum insulin concentrations were significantly higher in the NC and GNH groups compared to the DBC, GNL, and GRL groups, while no significant difference was observed for the GRH group. Better glucose tolerance was observed in the GNH group compared to the DBC and all other ginger- and garlic-fed groups. Final body weight, fasting blood glucose, blood glycated hemoglobin, liver weight, liver glycogen levels, and serum lipid profiles were not influenced by the ginger- or garlic-containing diet. Data of this study suggest that ginger and garlic are insulinotropic rather than hypoglycemic while overall anti-diabetic effects of ginger are better than those of garlic, at least in this experimental condition. Much better anti-diabetic effects of ginger and garlic may be obtained when feeding is with a normal rather than a HF-containing diet.