OBJECTIVE: To evaluate the effects of varying the glycemic index (GI) of carbohydrate-rich foods on metabolic control in type 2 diabetic patients. RESEARCH DESIGN AND METHODS: In a randomized crossover study, 20 patients, 5 women and 15 men, were given preweighed diets with different GIs during two consecutive 24-day periods. Both diets were composed in accordance with dietary recommendations for people with diabetes. The macronutrient composition and type and amount of dietary fiber were identical. Differences in GI were achieved mainly by altering the structure of the starchy foods. RESULTS: Peripheral insulin sensitivity increased significantly and fasting plasma glucose decreased during both treatment periods. There was a significant difference in the changes of serum fructosamine concentrations between the diets (P < 0.05). The incremental area under the curve for both blood glucose and plasma insulin was approximately 30% lower after the low- than after the high-GI diet. LDL cholesterol was significantly lowered on both diets, with a significantly more pronounced reduction on the low-GI diet. Plasminogen activator inhibitor-1 activity was normalized on the low-GI diet, (-54%, P < 0.001), but remained unchanged on the high-GI diet. CONCLUSIONS: A diet characterized by low-GI starchy foods lowers the glucose and insulin responses throughout the day and improves the lipid profile and capacity for fibrinolysis, suggesting a therapeutic potential in diabetes.