Objective To evaluate the present Chinese body mass index (BMI) criteria with body fat percentage (BF%) in determining obesity in Chinese population. Methods A total of 4 907 subjects (age: 20-90 yrs) were enrolled in the baseline survey of a longitudinal epidemiological study, and 2 638 of them were reevaluated in 5.5 years later. The Chinese BMI and WHO BF% were used to define obesity, respectively. Results The diagnostic agreement between the Chinese BMI and WHO BF% definitions for obesity was poor for both men (kappa: 0.210, 95% CI: 0.179-0.241) and women (kappa: 0.327, 95% CI: 0.296-0.358). However, BMI had a good correlation with BF% both in men (r: 0.785, P35% for women)(RR: 2.89, 95% CI: 1.43-5.81), or in subjects with high BMI (BMI≥28 kg/m2) (RR: 2.46, 95% CI: 1.31-4.63) when compared to those with low BF% (BF%≤20% for men and≤30% for women) or low BMI (BMI