OBJECTIVE: To develop a score to predict impaired glucose tolerance (IGT) using common clinical data. RESEARCH DESIGN AND METHODS: We analyzed data from the Third National Health and Nutrition Examination Survey (NHANES III) for 2,746 individuals aged 40-74 years who completed an oral glucose tolerance test. IGT was defined as a 2-h postchallenge glucose > or =140 mg/dl (7.7 mmol/l). We performed bivariate and multivariate analyses to describe the association of IGT with commonly available clinical information. A numerical score to predict IGT was derived from the results of the multivariate logistic regression models. RESULTS: Fasting glucose levels between 101 and 109 mg/dl (5.6 and 6.0 mmol/l) or between 110 and 125 mg/dl (6.1 and 6.9 mmol/l) were associated with IGT (odds ratio 1.8 and 6.2, respectively; P < 0.05). BMI > or =25 kg/m(2), Mexican-American ethnicity, age between 60 and 74 years, hypertension, and triglyceride level > or =150 mg/dl (1.69 mmol/l) were also associated with IGT. The area under the receiver operating characteristic curve for an 8-point scale derived from the multivariate analysis was 0.74 (95% CI 0.72-0.76). Setting a low cut point of 2 on this scale resulted in high sensitivity (86%), whereas a high cut point of 6 yielded high specificity (97%) for the detection of IGT. CONCLUSIONS: A numerical score based on common clinical data can identify individuals with a low or high likelihood of having IGT.