The radiologic tables used for many imaging procedures have maximum weight limits. Many United States (US) adults may have a body weight that exceeds these limits and may be ineligible for diagnostic imaging procedures. Using data from the National Health and Nutrition Examination Surveys in 1976 to 1980, 1988 to 1994, and 1999 to 2004, we determined the increase in the percentage and number of US adults weighing>or=300 pounds (i.e., the weight limit for an electron beam computed tomography table). In addition, the prevalence and clustering of 5 cardiovascular disease risk factors (current smoking, hypertension, diabetes mellitus, low high-density lipoprotein cholesterol, and elevated C-reactive protein) was determined for US adults weighing>or=300 pounds, and compared with their counterparts weighing<300 pounds. The percentage of US adults, >or=20 years, weighing>or=300 pounds was 0.10%, 0.79%, and 1.50% in 1976 to 1980, 1988 to 1994, and 1999 to 2004, respectively (p trend<0.001). This corresponds to an increase from 130,000 US adults weighing>or=300 pounds in 1976 to 1980, to 1,390,000 in 1988 to 1994 and 3,020,000 in 1999 to 2004 (p trend<0.001). After age standardization, in 1999 to 2004, 34.1% and 24.0% of adults weighing>or=300 pounds had 2 and >or=3, respectively, of the 5 cardiovascular disease risk factors, compared with 17.7% and 5.3%, respectively, of adults weighing<300 pounds (each p<0.001). In conclusion, morbid obesity has increased dramatically among US adults. The clustering of cardiovascular disease risk factors associated with morbid obesity and the exclusion from diagnostic imaging may affect those most in need of such procedures.