Objectives: To assess the independent effect of waist circumference on mortality across the entire body mass index (BMI) range and to estimate the loss in life expectancy related to a higher waist circumference. Patients and Methods: We pooled data from 11 prospective cohort studies with 650,386 white adults aged 20 to 83 years and enrolled from January 1, 1986, through December 31, 2000. We used proportional hazards regression to estimate hazard ratios (HRs) and 95% CIs for the association of waist circumference with mortality. Results: During a median follow-up of 9 years (maximum, 21 years), 78,268 participants died. After accounting for age, study, BMI, smoking status, alcohol consumption, and physical activity, a strong positive linear association of waist circumference with all-cause mortality was observed for men (HR, 1.52 for waist circumferences of ≥110 vs <90 cm; 95% CI, 1.45-1.59; HR, 1.07 per 5-cm increment in waist circumference; 95% CI, 1.06-1.08) and women (HR, 1.80 for waist circumferences of ≥95 vs <70 cm; 95% CI, 1.70-1.89; HR, 1.09 per 5-cm increment in waist circumference; 95% CI, 1.08-1.09). The estimated decrease in life expectancy for highest vs lowest waist circumference was approximately 3 years for men and approximately 5 years for women. The HR per 5-cm increment in waist circumference was similar for both sexes at all BMI levels from 20 to 50 kg/m2, but it was higher at younger ages, higher for longer follow-up, and lower among male current smokers. The associations were stronger for heart and respiratory disease mortality than for cancer. Conclusions: In white adults, higher waist circumference was positively associated with higher mortality at all levels of BMI from 20 to 50 kg/m 2. Waist circumference should be assessed in combination with BMI, even for those in the normal BMI range, as part of risk assessment for obesity-related premature mortality.