The efficacy and safety of sitagliptin as monotherapy were evaluated in Chinese, Indian, and Korean patients with type 2 diabetes inadequately controlled by diet and exercise. In a randomized, placebo-controlled, double-blind, 18-week trial, 530 patients with HbA(1c) >or=7.5% and <or=11.0% (mean baseline 8.7%) received sitagliptin 100mg once daily or placebo. Compared with placebo, sitagliptin significantly (p<0.001) reduced mean HbA(1c) (-1.0%), fasting plasma glucose (-1.7 mmol/L), and 2-h postprandial glucose (-3.1 mmol/L), and a significantly (p<0.001) greater proportion of sitagliptin-treated versus placebo-treated patients achieved HbA(1c) <7% (20.6% versus 5.3%, respectively) at study end. Efficacy of sitagliptin was demonstrated in each country. Sitagliptin was generally well-tolerated. Clinical adverse events (AEs) were reported in 23.3% and 15.2% of sitagliptin-treated and placebo-treated patients, respectively. The difference was primarily due to increased gastrointestinal AEs in the sitagliptin group, most of which were mild and resolved on study drug. Serious AEs, discontinuations due to AEs, and drug-related AEs occurred with a low incidence in both groups. No hypoglycemia was reported. In conclusion, in this study, sitagliptin monotherapy for 18 weeks significantly improved glycemic control and was well-tolerated in patients with type 2 diabetes from China, India, and Korea.