Objective: This paper aims to describe the preliminary development of a scale of parental efficacy for parents participating in the Maudsley model of family-based treatment. The purpose of this scale is to provide a means of testing the effect of new and augmentative therapeutic strategies in the Maudsley model on the development of parental efficacy over time. Method: Forty-nine parents of patients with anorexia nervosa completed a preliminary version of the Parents Versus Anorexia. Scale (PVA). They also completed the Rotter I/E Scale and the Family Adaptability and Cohesion Evaluation Scale II (FACES II) as comparison measures. Measures of total increase in percentage ideal body weight (%IBW) were taken for the children of 34 of these parents who were participating in family-based treatment. Comparisons were also made between mean PVA scores of parents waiting for treatment and those whose children had gained significant weight as a result of treatment. Results: The Cronbach's alpha for the final seven items of the PVA was 0.78. The scale also has a significant positive correlation with internal control as measured by the Rotter I/E Scale and with the total increase in %IBW that parents had been able to achieve for their children in the process of treatment. FACES II was not sensitive enough to measure differences in family structure for the purpose of this study. A significant difference was found between PVA scores of parents waiting for treatment and those of parents of patients who had gained greater than 10% of ideal body weight as a result of treatment. Discussion: These results provide preliminary support for the Parents Versus Anorexia Scale and as such this study represents the first attempt to design a measure specifically for the Maudsley model of family-based treatment.