One hundred and thirty‐three obese women were administered a modified version of the Reid‐Ware Locus of Control questionnaire prior to jaw wiring. The factorial structure of the questionnaire was examined, and found to be primarily a unidimensional measure of internal and external locus of control, with two subscales. Total score had greatest predictive validity in terms of the four criteria of success of weight loss while wired, percentage weight loss of wiring weight, weight gain over six months, and compliance with the treatment régime. Twenty items of the scale predicted success on one or more of these criteria of success, and are presented as an abbreviated locus of control scale with a higher degree of validity than the original s