Objective To develop a high-performance liquid chromatographic/tandem mass spectrometry (HPLC-MS/MS) method for the determination of plasma methylglyoxal and glyoxal concentrations in patients with diabetes mellitus. Methods HPLC-MS/MS method was employed to measure the plasma methylglyoxal and glyoxal concentrations in patients with type 1 diabetes mellitus (n=15) and type 2 diabetes mellitus (n=17) and normal subjects (n=10). 2,3-diaminonaphthalene (2,3-DAN) and hexanedione (using as internal standard) were added to plasma samples. After sufficient reaction and precipitation with acetonitrile from the plasma, methylglyoxal-DAN, glyoxal-DAN and hexanedione-DAN were isolated chromatographically on a Hypersil GOLD column (50 mm×2.1 mm, 5 μm). The mobile phase consisted of acetonitrile-0.1% formic acid (57∶43, v/v). Electrospray ionization source was applied and operated in the positive ion mode. The transitions of m/z 195.18→m/z 126.25, m/z 181.14→m/z 126.10 and m/z 237.34→m/z 209.34 were used to quantify methylglyoxal-DAN, glyoxal-DAN and hexanedione-DAN respectively. Results The linear calibration curves were obtained in the concentration range of 2-1 000 ng/mL and 50-1 000 ng/mL for methylglyoxal-DAN and glyoxal-DAN respectively. The average recovery rate was more than 70%. The plasma methylglyoxal and glyoxal concentrations in patients with type 1 and type 2 diabetes mellitus were significantly higher than those in normal subjects. Conclusion The established HPLC-MS/MS method is proved to be suitable for determination of plasma methylglyoxal and glyoxal concentrations in patients with diabetes mellitus, which offers advantages of high sensitivity and selectivity.