OBJECTIVE: To examine the diabetes risk association with femur length, standing height, and height without femur length (HWFL) (HWFL = standing height--femur length). RESEARCH DESIGN AND METHODS: We used data from three time periods of the National Health and Nutrition Examination Survey (1999-2000, 2001-2002, and 2003-2004) for this cross-sectional analysis and confined the eligible subjects to 6,188 adults aged 20+ years who had fasted >or=8 h and had no missing values of femur length or standing height. The outcome measure was type 2 diabetes. RESULTS: Multivariate logistic regression analyses indicated that the odds of type 2 diabetes per 1-SD value increase in femur length, standing height, and HWFL were 0.73 (95% CI 0.61-0.86), 0.91 (0.75-1.10), and 1.09 (0.90-1.32) for men, respectively, and 0.82 (0.70-0.97), 0.99 (0.82-1.21), and 1.11 (0.93-1.33) for women. CONCLUSIONS: Our study supports the hypothesis that femur length may be the key height component in diabetes risk association.