Rotter's (1966) concept of locus of control is the general tendency to believe that what happens to us depends on ourselves (internality) or, conversely, on chance or other factors beyond our control (externality). The main aim of this study was to show the prognostic value of the LOC and the value of psychotherapeutic action aimed at increasing the belief in personal control in the treatment of obesity. A comparison was made between the different general locus scales. Subjects were classified according to the presence or absence of eating disorders. The population consisted of 46 obese women undergoing treatment at a hospital in Bordeaux, France. The results showed that eating behaviour disorders in obese people are linked to externalism in weight control and externalism in personal control. Obese subjects without BAC believed more in weight control and personal control than subjects with BAC.