The objective of this study was to investigate the efficacy, tolerability, and safety of acarbose in the improvement of glycemic control in Asian patients with type 2 diabetes inadequately controlled by diet and sulfonylureas. A 24-week, double-blind, placebo-controlled multicenter group comparison study was conducted. Patients were randomized to receive acarbose titrated up to 100-mg tid (n=36) or matching placebo (n=33). Concomitant sulfonylurea treatment remained unchanged throughout the study. The primary efficacy parameter was the change in HbA(1c) from baseline to double-blind endpoint. Secondary efficacy variables consisted of the change from baseline to endpoint in blood glucose (fasting and 1-h postprandial), serum insulin (fasting and 1-h postprandial), and urinary glucose. In the intention-to-treat (ITT) analysis, acarbose treatment was associated with significantly greater reductions in glycated hemoglobin (HbA(1c)) (-0.91% vs. placebo 0.13%, P=.0018) and 1-h postprandial blood glucose levels (-2.84 mmol/l vs. placebo -0.28 mmol/l, P=.002) compared to placebo. There were no significant differences between the treatment groups regarding changes in fasting blood glucose, fasting or 1-h postprandial serum insulin, urinary glucose, or body weight. Adverse events occurred with similar frequency in both treatment arms except for drug-related gastrointestinal side-effects associated with acarbose (acarbose 48.5% and placebo 12.5%). This study has shown that the use of acarbose in Asian patients with type 2 diabetes inadequately controlled by diet and sulfonylureas is efficacious in improving metabolic control and that acarbose is safe and well tolerated.