The aim of this study was to evaluate the efficacy of acarbose, an inhibitor of α-glucosidase, on glycemic control in elderly overweight type 2 diabetic patients poorly controlled by oral hypoglycemic agents (OHA) or insulin. Our study included 22 overweight patients, 60–75-years-old, treated with OHA and/or insulin who, after a period of 4 weeks of controlled diet, showed a poor metabolic control. They were divided into two groups: Group I (nine patients) on OHA treatment; Group II (13 patients) undergoing treatment with insulin alone or in combination with OHA. Acarbose was administered to all the patients (100 mg three times a day at meal times) for 6 months in addition to their previous treatment. The addition of acarbose caused a significant reduction in both groups with regard to fasting glycemia (after 3 and 6 months, respectively, 20.7 and 21.9%, P<0.04 in Group I; 19.1 and 21.8%, P<0.04 in Group II), and postprandial glycemia (after 3 and 6 months, respectively, 41.6 and 42.5%, P<0.0001 in Group I; 35.6 and 38%, P<0.0006 in Group II). There was also a significant reduction in the values of HBA 1c in Group I after 6 months of treatment (24.3%, P<0.05) and in Group II after 3 and 6 months (respectively 13.4%, P<0.02 and 20.6%, P<0.01). Three months after treatment with acarbose ended, fasting and postprandial glycemia and HBA 1c values returned to original baseline values. In conclusion, the addition of acarbose to the OHA in elderly overweight type 2 diabetic patients poorly controlled by OHA or insulin regimes improved metabolic control.