The purpose of this project was to determine whether registered dietitians (RDs) exhibit a negative bias toward obese persons. The participants (n = 175) comprised a convenience sample of RDs from professional listservs, resulting in 128 (73%) completed surveys. The researchers used the Fat People-Thin People Implicit Association Test, found on the Web site: www.implicit.harvard.edu (designed to measure social knowledge). Bivariate associations were tabulated and an F test was performed to find association among variables. Across all categories, RDs (n = 98; 76%) had a strong to moderate preference (P = .05) for thin people in comparison with fat people, which exceeded the Implicit Associations Test results taken from the general population (n = 2.5 million; 52%). Registered dietitians tended to be less tolerant of obesity than those among the general population. Education for RDs on improving tolerance with individuals who are obese is recommended, especially for RDs who counsel overweight patients.