We champion the view that a richer understanding of electronic markets is obtained when their implications for consumers are jointly studied from social, economic, and psychological perspectives. We adopt this perspective triad to build a Social-Economic-Psychological (SEP) Model of technology adoption and usage, and apply the model to understand and explain the behavior of online investors. The SEP model provides a foundation for a multidisciplinary approach to the study of electronic markets and online consumers in the fields of MIS, marketing, and finance.