Objective: Some studies have shown that abdominal obesity may be a better predictor than overall obesity for disease risks and all‐cause mortality. This study sought to examine the recent trends in waist circumference (WC) among adults in the United States.

Research Methods and Procedures: Data from the National Health and Nutrition Examination Survey during 1988–1994, 1999–2000, 2001–2002, and 2003–2004 were analyzed to estimate the trends in the mean WC and the prevalence of abdominal obesity. Pooled t tests were used to test the differences in estimates between two time periods.

Results: Between the periods of 1988–1994 and 2003–2004, the age‐adjusted mean WC increased from 96.0 cm to 100.4 cm among men (p < 0.001) and from 89.0 cm to 94.0 cm among women (p < 0.001); the age‐adjusted prevalence of abdominal obesity increased from 29.5% to 42.4% among men (p < 0.001) and from 47.0% to 61.3% among women (p < 0.001). Between the periods of 1999–2000 and 2003–2004, a significant increase occurred in mean WC only among men (from 99.0 cm to 100.4 cm; p = 0.03) and in the prevalence of abdominal obesity among both men (from 37.0% to 42.2%; p = 0.03) and women (from 55.3% to 61.3%; p = 0.04). People with a BMI of 25 to 29 kg/m² had a greater relative increase in abdominal obesity.

Discussion: The mean WC and the prevalence of abdominal obesity among U.S. adults have increased continuously during the past 15 years. Over one‐half of U.S. adults had abdominal obesity in the period of 2003–2004.