OBJECTIVE: To evaluate the dipeptidyl peptidase-4 (DPP-4) inhibitor alogliptin in drug-naïve patients with inadequately controlled type 2 diabetes. RESEARCH DESIGN AND METHODS: This double-blind, placebo-controlled, multicenter study included 329 patients with poorly controlled diabetes randomized to once-daily treatment with 12.5 mg alogliptin (n = 133), 25 mg alogliptin (n = 131), or placebo (n = 65) for 26 weeks. Primary efficacy end point was mean change from baseline in A1C at the final visit. RESULTS: At week 26, mean change in A1C was significantly greater (P < 0.001) for 12.5 mg (-0.56%) and 25 mg (-0.59%) alogliptin than placebo (-0.02%). Reductions in fasting plasma glucose were also greater (P < 0.001) in alogliptin-treated patients than in those receiving placebo. Overall, incidences of adverse events (67.4-70.3%) and hypoglycemia (1.5-3.0%) were similar across treatment groups. CONCLUSIONS: Alogliptin monotherapy was well tolerated and significantly improved glycemic control in patients with type 2 diabetes, without raising the incidence of hypoglycemia.