Abstract The purpose of this investigation is to identify the anticipatory reward mechanisms that maintain bulimic behavior in bulimia nervosa. Emerging data indicate the importance of reward and anticipatory processes as maintenance mechanisms of bulimia nervosa that can be targeted in existing and novel treatments. The proposed research will identify neurobiological and psychological anticipatory mechanisms of bulimic behavior using fMRI as well as ecological momentary assessment (EMA) in the natural environment. In this investigation, 60 adults (30 with bulimia nervosa and 30 comparison participants) will undergo negative and positive mood inductions followed by an fMRI food selection task (and a comparison shopping task) to examine neurobiological and affective responses to behavior anticipation. Because these anticipatory processes are hypothesized contributors to illness maintenance, duration of illness will be examined as a moderator. To examine the ecological validity of our fMRI results, participants with bulimia nervosa will complete two weeks of ecological momentary assessment (EMA) examining real-time affect changes in relation to the anticipation of bulimic behavior. These methods will facilitate rigorous assessment of the links between neurobiological (fMRI) and naturalistic (EMA) data in anticipatory reward processes. Findings from this investigation will inform the conceptualization and treatment of bulimia nervosa by identifying the role of reward anticipation in symptom maintenance, providing a crucial framework for targeting these anticipatory processes in the existing and novel interventions.