OBJECTIVE Recent reports suggest that dietary energy density may play a role in regulation of food intake. However, little is known about the energy density of diets consumed by free-living populations; therefore, the purpose of this study was to examine demographic, health, and nutritional correlates of energy density of self-reported diets. METHODS Using data from the NHANES III (n=13 400), dietary energy density was defined three ways: (1) energy content (kJ/g) of all foods and beverages reported or ED1, (2) energy content (kJ/g) of all foods and energy yielding beverages or ED2, and (3) energy content (kJ/g) of all foods (no beverages) or ED3. Multiple linear or logistic regression methods were used to examine the association of energy density with intake of energy, nutrients, food groups, and body mass index (BMI). We computed the ratios of within- to between-person variance for the three energy density variables using the second recall obtained from the second exam subsample of NHANES III (n=1037). RESULTS The mean ED1, ED2, and ED3, respectively, were 3.84+/-0.02, 5.45+/-0.03, and 8.03+/-0.03. Dietary intakes of energy, fat, and low-nutrient-density foods were related positively, but amounts of micronutrients, fruit, and vegetables were related inversely with all types of energy density (P<0.0001). ED2 and ED3 were modest positive predictors of BMI in both men and women (P< or =0.03). The ratios of within- to between-person components of variance for ED1, ED2, and ED3 were 1.34, 2.05, and 1.53, respectively. CONCLUSIONS High-energy-density diets in the US were characterized by low fruit and vegetable intake, and high BMI.