Obesity is a strong determinant of blood pressure. Uncertainty remains, however, about which indices of adiposity most strongly predict blood pressure, particularly among those who were relatively lean, such as those from rural China. We analyzed cross-sectional data on 55 ,687 (38.3% men) participants aged 30-79 years who were enrolled into the China Kadoorie Biobank from a rural county in southwest of China during 2004-2008. Measured body mass index (BMI) and waist circumference (WC) were related to blood pressure in multivariable linear regression analyses. The overall mean values of BMI, WC, systolic blood pressure (SBP) and diastolic blood pressure (DBP) were 23.3 kg m(-2), 78.0 cm, 129.2 mm Hg and 77.2 mm Hg, respectively. There was a strongly positive, and apparently linear, relationship of BMI and WC with blood pressure, with 1 s.d. higher BMI associated with 4.3/2.3 mm Hg higher SBP/DBP and 1 s.d. WC associated with 3.8/2.1 mm Hg (P<0.0001). Additional adjustment for WC only slightly attenuated the association of BMI with blood pressure, whereas additional adjustment for BMI almost completely eliminated the association of WC with blood pressure. Our findings suggest that in relatively lean Chinese adults, general adiposity is more strongly assciated with blood pressure than central adiposity.