An eight-week weight-loss competition was conducted in an industrial worksite in Big Island, Virginia in the spring of 1993. Educational interventions were based on theories of self-efficacy and social support. Sixteen employees volunteered for the weight loss competition; fifteen completed the program. A single case study design was used to analyze the relationships among self-efficacy, intake of dietary fat, and weight loss as impact variables. Process variables deemed important for the program’s success were also examined for each individual. They included attendance at weekly weigh-ins, completion of daily food intake forms, attendance at weekly educational sessions, and completion of self-efficacy questionnaires. Results showed that women were more likely to participate in the program’s activities than men. Teams that worked together (within the same department) were more successful and more supportive of each other than teams composed of individuals from different departments. Individuals who participated in the educational sessions and competed in the assignments were more successful in losing weight. Due to the small number of participants, no significant effect was found between self-efficacy scores and weight loss. / Master of Science