This dissertation studies the antecedents and consequences of the flow experience in online retailing environments. Flow is the enjoyable and engrossing experience that people feel when acting with total involvement. A review of previous studies suggests that applying the notion of flow to understand the online consumer experience is a promising but underdeveloped field with several conceptual and methodological issues. This dissertation attempts to contribute to our understanding of flow in online shopping in three ways. First, a three-part validity study was carried out using different approaches to construct validity and involving two sets of two flow measures: the Flow State Scale (FSS, Jackson and Marsh 1996) and the Internet Flow Scale (IFS). The first study related flow to behavioral criteria in online shopping. The second conducted a traditional construct validity study in which we developed and tested a “nomological network” of relationships between flow measures and other logically-related constructs. This study also included a Multitrait-Multimethod validity study. The third was a factorial validity study of the flow construct. These studies provided evidence of construct validity for flow and suggested that the FSS had advantages over the IFS in terms of validity. Second, this dissertation tested a comprehensive model of flow that included the underlying dimensions of flow, the mediating effects of perceived challenge and skill on flow, and antecedents and consequences of flow. Consequences of flow include perceived usefulness, affective responses to the site, and intentions to revisit and purchase. Overall, results based on data collected by a controlled experiment supported our model, suggesting that flow is a second-order construct and positively related to outcome variables. Thirdly, we studied the effect of Web site complexity on flow. Perceived site complexity was found to effect flow negatively. Investigating the effects of it on inducing flow in online shopping may eventually lead us to guidelines for improving the shopping experience by designing more capable Web sites.