Serum insulin and blood metabolite responses to oral glucose with and without intravenous naloxone were measured in 24 chlorpropamide-alcohol flush positive and negative Type 2 (non-insulin dependent) diabetic patients with and without retinopathy. In the chlorpropamide-alcohol flush positive patients with retinopathy, fasting blood glucose was increased greater than 40% and the serum triglycerides were increased over twofold compared with each of the other three groups. Following oral glucose (50 g), the chlorpropamide-alcohol flush positive diabetic patients with complications had a lower serum insulin and higher blood glycerol than the other three groups. Thus, chlorpropamide-alcohol flush positive subjects with retinopathy showed distinct metabolic differences from the other three groups. There was no evidence that opiate-receptors influenced the metabolic response to oral glucose in the Type 2 diabetic patients since the infusion of intravenous naloxone produced no effect on the serum insulin or blood metabolites.