Although the stigma of obesity in our society is well documented, the measurement of antifat attitudes has been a difficult undertaking. Two studies were conducted to construct and validate the Antifat Attitudes Test (AFAT). In study 1, college students (110 men and 175 women) completed the preliminary 54-item AFAT and specific indices of body image and weight-related concerns. Psychometric and factor analysis revealed a 47-item composite scale and three internally consistent factors that were uncorrelated with social desirability: Social/Character Disparagement, Physical/Romantic Unattractiveness, and Weight Control/Blame. Several body images correlates of antifat prejudice were identified, and men expressed more negative attitudes than women. Study 2 experimentally examined the effects of information about the controllability of weight on the antifat attitudes of 120 participants. Exposure to information on behavioral vs. biogenetic control led to greater blame of persons who are fat for their body size. The implications of the findings and the potential utility of the AFAT are discussed.