 We performed a prospective, randomized, multicenter trial to assess the efficacy and safety of combined treatment with mitiglinide and metformin for patients with type 2 diabetes who show inadequate glycemic control with metformin monotherapy. Subjects with HbA1c 7.0 after an 8-week metformin run-in phase were randomized to a 16-week trial phase with metformin plus mitiglinide MetMit or metformin plus placebo Met. 