OBJECTIVE: The purpose of this study was to determine the baseline predictors of new-onset diabetes (NOD) in hypertensive patients and to develop a risk score to identify those at high risk of NOD. RESEARCH DESIGN AND METHODS: Among 19,257 hypertensive patients in the Anglo-Scandinavian Cardiac Outcomes Trial-Blood Pressure Lowering Arm (ASCOT-BPLA) who were randomly assigned to receive one of two antihypertensive regimens (atenolol +/- thiazide or amlodipine +/- perindopril), 14,120 were at risk of developing diabetes at baseline. Of these, 1,366 (9.7%) subsequently developed NOD during median follow-up of 5.5 years. A multivariate Cox model was developed to identify the independent predictors of NOD and individual risk scores. RESULTS: NOD was significantly associated with an increase in baseline fasting plasma glucose (FPG), BMI, serum triglycerides, and systolic blood pressure. In contrast, amlodipine +/- perindopril in comparison with atenolol +/- thiazide treatment (hazard ratio 0.66 [95% CI 0.59-0.74]), high HDL cholesterol, alcohol use, and age >55 years were found to be significantly protective factors. FPG was the most powerful predictor with risk increasing by 5.8 times (95% CI 5.23-6.43) for each millimole per liter rise >5 mmol/l. The risk of NOD increased steadily with increasing quartile of risk score, with a 19-fold increase (95% CI 14.3-25.4) among those in the highest compared with those in the lowest quartile. The model showed excellent internal validity and discriminative ability. CONCLUSIONS: Baseline FPG >5 mmol/l, BMI, and use of an atenolol +/- diuretic regimen were among the major determinants of NOD in hypertensive patients. The model developed from these data allows accurate prediction of NOD among hypertensive subjects.