It was reported that Hcy was related to the development of kidney disease, but it remains unknown whether Hcy is an independent biomarker for diabetic nephropathy. Analytical method for simultaneous determination of aminothiols among the Hcy metabolic cycle is desirable to discover other potential biomarkers. A high-performance liquid chromatography-electrospray tandem mass spectrometric (HPLC-ESI-MS/MS) method was established for simultaneous quantitation of Cysteine (Cys), total homocysteine (tHcy). S-adenosylrnethionine (SAM), S-adenosylhomocysteine (SAH), cystathionine (Cysta), methionine (Met), glutathione (GSH) and cysteinylglycine (Cys-gly) in plasma with N-(2-mercaptopropionyl)-glycine (MPG) as internal standard. The method had simple pretreatment without derivatization and the chromatograms show better separation of the eight aminothiols and the analytic time was 20 min. The results demonstrated that it provided an excellent linearity for all analytes over their respective concentration ranges and illustrated excellent precision and plasma recovery as well. Then, the method was applied in the case-control study of patients with diabetes mellitus (DM) and diabetic nephropathy (DN). In conclusion, it is an effective method to quantitate the concentrations of aminothiols in the human plasma. SAH and SAM were suggested as better potential biomarkers; of DM and DN. (C) 2008 Elsevier B.V. All rights reserved.