OBJECTIVE: To determine if energy intake underreporting concerns all major food groups or if it occurs for speci®c food groups only. DESIGN: Cross-sectional study on dietary habits and food consumption. SUBJECTS: Five-hundred and four women and 529 men, aged between 25 and 55 y participating in the Fleurbaix Laventie Ville Sante  study. MEASUREMENTS: A nutritional survey was conducted between March and June 1993 using a 3-day food record. Reported weight and height were used to estimate body mass index and basal metabolic rate. Underreporters were de®ned as subjects whose ratio of mean energy intake to basal metabolic rate was lower than 1.05. Food consumption was compared between underreporters and non-underreporters. RESULTS: Energy percentage of fat and carbohydrate were lower in underreporters than in non-underreporters in contrast to the energy percentage of protein. This was due to the fact that food items rich in fat andaor carbohydrates (such as butter, French fries, sugars and confectionery, cakes and pastries) were reported to be less frequently eaten andaor in smaller quantities in underreporters compared to non-underreporters. CONCLUSION: Although this study presents some limitations, like the use of reported weight and a standard value for physical activity, it shows that reported foods differed, quantitatively and qualitatively, between severe underreporters and non-underreporters. Underreporting of food intake does not result from a systematical underestimation of portion sizes for all food items, but seems to concern speci®c food items which are generally considered `bad for health'.