Dietary assessment is an integral component of the determination of medical, nutritional and educational needs of bulimic individuals. The ability to accurately assess portion size is an important aspect of dietary assessment, but may be altered in bulimics due to changes in visual perception and food beliefs. We surveyed 132 bulimic female subjects who were enrolled in an eating disorder treatment program to determine the accuracy with which they could estimate portion sizes of 25 commonly consumed foods. Subjects were also asked to provide data on their height, weight, previous food measurement experience and the "safety" factor with which they could eat each food item. The mean percent error was >50% for 20 foods and > 100% for 5 foods. Estimations of over 301% were made by 66 subjects. Estimations of greater than 500% were made by 20 subjects. No relationship of accuracy to age of subject was noted. Body Mass Index status was related to only one food (X2= 10.31, p=0.03). Previous experience in measuring foods was related to 2 food items (X2= 13.17, p=0.02; X2=29.84, p=0.00). There was a trend for those foods which were considered "dangerous" or unsafe to be overestimated by subjects. Our results suggest that the ability of bulimic subjects to estimate portion sizes may be affected by the psychological safety factor associated with that food and, to a lesser extent, any previous experience in measuring foods. These factors should be considered when assessing the dietary intakes of bulimic subjects.