Objective This study was designed to identify determinants of body size perceptions and their relationship to dietary behavior in a multiethnic group of women.Design A single interview consisting of the Massara and Stunkard body image cards (1979) and questionnaires on sociocultural background, anthropometry, and dieting history were administered to volunteers from the staff of a hospital.Subjects The sample was a convenience sample of 186 women representing a range of staff positions recruited from Methodist Hospital in Brooklyn, NY; 174 completed the study. Data on 150 women are presented in this article.Results Height and weight-for-height were stronger predictors of accuracy of perceived body size than ethnicity. Tall, slight women were more likely to overestimate and short, heavy women were more likely to underestimate actual body size. Ethnicity had an interactive effect with height as taller European Americans were more likely to perceive their body size as larger than actual compared with Afro-Caribbeans and African Americans. Women with a history of dieting were more likely to overestimate their size and to view it as different from what is perceived as attractive to others.Applications/conclusions Based on the results, we conclude that body size is a stronger predictor of accuracy of perceived body size than ethnicity; and dieters overestimate their body size and believe it to be heavier than their social group would prefer. J Am Diet Assoc. 1996; 96:252-256.