This study examined the plausibility of models we proposed to explain eating behavior. Self-efficacy was a key factor in the models and was postioned as a mediator between environmental social factors (family and friend support) and eating behavior. We proposed that the environmental factors could directly influence eating behavior or indirectly influence it through self-efficacy which could, in turn, directly influence eating behavior or indirectly influence it through outcome expectancy. Data used in examining the models were obtained from 170 women who participated in a 10 week weight control course. Data collected prior to the course (Time 1), immediately after it (Time 2) and 2 months afterward (Time 3) were used respectively to test models for each time period with the number of subjects having complete data at each time period being 170, 120 and 107, respectively. Analyses did not confirm any of the proposed full models, but in reduced models, self-efficacy contributed significantly to explanation of eating behavior at Time 1 and to eating behavior change at Time 3. At Time 1, friend support indirectly influenced eating behavior acting through self-efficacy; at Time 3 family and friend support influenced eating behavior both directly and indirectly through self-efficacy. Contributions of outcome expectancy were inconsistent and weak. Results indicate that self-efficacy may be an important factor to address in nutrition education programs designed to change eating behavior.