Objective: Identifying GAD-Ab and quantitating C-Peptide were to evaluate the pancreatic  - cell function in patients with newly diagnosed type 2 diabetes. Method: Descriptive - cross sectional - prospective study was conducted on 100 Vietnamese patients with newly diagnosed type 2 diabetes (12 males and 88 females), aged from 36 to 75 and 46 Vietnamese without diabetes (7 males and 39 females), aged from 30 to 69.