The anti-hyperglycemic effect of alpha-glucosidase inhibitors (AGI) is partly attributed to their ability to stimulate the secretion of glucagon-like peptide-1 (GLP-1), a gut hormone with insulin stimulating capability. To determine if this mechanism of action contributes significantly to the therapeutic efficacy of AGI in the elderly, 10 type 2 diabetic subjects over the age of 65 years were given a standardized test meal with or without 25, 50, or 100 mg acarbose. The serum glucose, insulin, triglycerides and GLP-1 levels were measured at baseline and at 1 and 2 h postprandially. The anti-hyperglycemic effect of acarbose was maximal at 25-mg dose under these experimental conditions. Serum postprandial insulin and triglycerides levels were not significantly altered with acarbose treatment. The postprandial serum GLP-1 levels rose significantly only in two subjects and only during treatment with 100-mg acarbose. There were no significant correlations between serum GLP-1 and serum glucose or insulin levels. It is concluded that in most elderly type 2 diabetic subjects, maximal anti-hyperglycemic effects can be achieved with relatively small doses of acarbose and that GLP-1 is unlikely to contribute to the clinical efficacy of this agent in this subgroup of subjects.