Self-efficacy theory proposes that beliefs about behavior are important variables to consider in the study of behavior change. The belief that an individual is capable of executing behavior and that the execution of such behavior will result in the desired outcome must be present for behavioral and psychological change to occur. This theory may have useful implications for the behavioral or cognitive-behavioral treatment of obesity. Sixty women and nine men participated in a weight-control program. Subjects were randomly assigned to behaviorally oriented intervention conditions which either did or did not contain a cognitive component. The hypothesis that greater changes in eating self-efficacy would be evident in the intervention conditions which contained a cognitive intervention component was not supported, although the pattern of the means was indicative of an increased effect in the cognitive groups. The hypothesis that there would be a significant relationship between weight loss and eating self-efficacy was supported; stronger evidence was derived from number of pounds lost than from a weight reduction quotient. Eating self-efficacy was significantly positively correlated with measures of hopelessness, motivation, stimulus control, and negative thoughts about weight and was negatively correlated with behavioral techniques. (Author/ABL)