The postprandial blood glucose and serum insulin responses to liquid test meals containing 40 g carbohydrate from milk, lactose, glucose or fructose and equal amounts of energy were compared in 10 non-insulin-dependent (type 2) diabetic patients. The meals were consumed in random order on consecutive days after an overnight fast. Significant differences (p less than 0.001, ANOVA) were observed between the glucose and insulin responses to the meals. The glucose response was significantly higher after the glucose containing meal and lower after the fructose meal as compared with the other meals. The insulin response was significantly higher after the lactose and glucose meals than after the milk and fructose meals. After the milk and lactose meals the blood glucose responses were similar whereas the insulin response was significantly lower after the milk meal. As lactose apparently was similarly absorbed from the two meals the difference in the insulin response was probably due to different insulinogenic effects of the protein components or to differences in the physical properties of the respective meals.