OBJECTIVE: To find clinically meaningful preoperative predictors of diabetes remission and conversely inadequate glycemic control after gastric bypass surgery. Predicting the improvement in glycemic control in those with type 2 diabetes after bariatric surgery may help in patient selection. RESEARCH DESIGN AND METHODS: Preoperative details of 154 ethnic Chinese subjects with type 2 diabetes were examined for their influence on glycemic outcomes at 1 year after gastric bypass. Remission was defined as HbA(1c) ≤6%. Analysis involved binary logistic regression to identify predictors and provide regression equations and receiver operating characteristic curves to determine clinically useful cutoff values. RESULTS: Remission was achieved in 107 subjects (69.5%) at 12 months. Diabetes duration <4 years, body mass >35 kg/m(2), and fasting C-peptide concentration >2.9 ng/mL provided three independent preoperative predictors and three clinically useful cutoffs. The regression equation classification plot derived from continuous data correctly assigned 84% of participants. A combination of two or three of these predictors allows a sensitivity of 82% and specificity of 87% for remission. Duration of diabetes (with different cutoff points) and C-peptide also predicted those cases in which HbA(1c) ≤7% was not attained. Percentage weight loss after surgery was also predictive of remission and of less satisfactory outcomes. CONCLUSIONS: The glycemic response to gastric bypass is related to BMI, duration of diabetes, fasting C-peptide (influenced by insulin resistance and residual β-cell function), and weight loss. These data support and refine previous findings in non-Asian populations. Specific ethnic and procedural regression equations and cutoff points may vary.