OBJECTIVE -To assess the efficacy of 1-h plasma glucose concentration and the metabolic syndrome in predicting future risk of type 2 diabetes. RESEARCH DESIGN AND METHODS - A total of 1,611 subjects from the San Antonio Heart Study, who were free of type 2 diabetes at baseline; who had plasma glucose and insulin concentrations measured at time 0,30, 60, and 120 min during the oral glucose tolerance test (OGTT); and who had their diabetes status determined with an OGTT after 7-8 years of follow-up, were evaluated. Two models, based on glucose tolerance status, 1-h plasma glucose concentration, and presence of the metabolic syndrome, were tested in predicting the risk for type 2 diabetes at 7-8 years of follow-up. RESULTS - A cutoff point of 155 mg/dl for the 1-h plasma glucose concentration during the OGTT was used to stratify subjects in each glucose tolerance group into low, intermediate, and high risk for future type 2 diabetes. A model based upon 1-h plasma glucose concentration, Adult Treatment Panel (ATP) III criteria for the metabolic syndrome, and fasting plasma glucose, independent of 2-h plasma glucose, performed equally well in stratifying nondiabetic subjects into low, intermediate, and high risk for future type 2 diabetes and identified a group of normal glucose-tolerant subjects who were at very high risk for future type 2 diabetes. CONCLUSIONS - The plasma glucose concentration at 1 h during the OGTT is a strong predictor of future risk for type 2 diabetes. A plasma glucose cutoff point of 155 mg/dl and the ATP III criteria for the metabolic syndrome can be used to stratify nondiabetic subjects into three risk groups: low, intermediate, and high risk.