This 24-week double-blind, randomized, multicenter, placebo-controlled, parallel-group study was performed in 632 drug-naïve patients with type 2 diabetes to assess efficacy and tolerability of vildagliptin (50 mg qd, 50 mg bid, or 100 mg qd). HbA1c decreased modestly in patients receiving placebo (Δ=-0.3±0.1%) and to a significantly greater extent in patients receiving vildagliptin 50 mg qd (Δ=-0.8±0 .1%), 50 mg bid (Δ=-0.8±0.1%), or 100 mg qd (Δ=-0.9±0.1%, pvs. placebo) from an average baseline of 8.4%. In patients diagnosed ≥3 months before enrollment, HbA1c increased with placebo (Δ=+0.2±0.2%) and between-treatment differences (vildagliptin-placebo) were -0.8±0.2% (p<0.001), -0.7±0.2% (p=0.003), and -0.9±0.2% (p<0.001) with vildagliptin 50 mg qd, 50 mg bid, and 100 mg qd, respectively. There was no apparent dose-response in the overall population; however, in patients with high baseline HbA1c, there were greater reductions with either 100 mg dose regimen (Δ=-1.3±0.2% and -1.4±0.2%) compared to 50 mg qd (Δ=-0.8±0.1%). Body weight decreased modestly in all groups (by 0.3 to 1.8 kg). The incidence of adverse events was similar across all groups and ≤1.2% of patients in any treatment group reported mild hypoglycemia. In conclusion, vildagliptin monotherapy decreases HbA1c in drug-naïve patients without weight gain and is well tolerated with minimal hypoglycemia.