A large portion of the American public is overweight and many are classified as being obese.  Obesity and unhealthy eating behavior are partially related to the increase in our society""s consumption of foods away from home. Accordingly, the Food and Drug Administration (FDA) has suggested new menu labeling regulations to help educate customers on healthy items among menu selections. Few studies have tried to understand customers"" healthy eating behavior in restaurants. Therefore, the purpose of this study was to understand and to predict customers' healthy eating behavior in casual dining restaurants, using the theory of planned behavior and the health belief model. The results showed that attitude toward healthy eating behavior and subjective norm positively influenced intention to engage in healthy eating behavior in casual dining restaurants while perceived behavioral control did not. For healthy eating behavior in casual dining restaurants, perceived threat, self-efficacy, response to provision of nutrition information (cue to action) were significant predictors. However, perceived benefits and barriers were not statistically significant. Also, the study found that subjective nutrition knowledge influenced customers' response to provision of nutrition information whereas objective nutrition knowledge did not. Customers' healthy eating behavior positively influenced their willingness to patronize a restaurant that offers healthy menu items, which means that those who try to eat healthy menu items in casual dining restaurants are willing to revisit restaurants where healthy menu choices are available and to recommend the restaurants to others. Finally, this study generated socio-demographic profiles related to healthy eating behavior in casual dining restaurants and willingness to patronize a restaurant that provides healthy menu choices. The results revealed that education levels and BMI (Body Mass Index) status influenced customers' healthy eating behavior. Also, customers' willingness to patronize a restaurant that provides healthy menu items differed based on gender, marital status, and education levels. / Ph. D.