This chapter analyzes the critical issues confronting usability for mobile commerce (m-commerce) applications. Limited bandwidth and multiple form factors pose constraints for user interface design in terms of the amount and format of content presentation, navigation, and site structure. Mobile tasks performed on handheld devices—such as wireless PDAs, Pocket PCs and WAP phones—challenge developers to adopt new methods and design guidelines that take into account contextual variations in a mobile environment. At this early stage of mobile commerce, careful mapping of e-business strategies, mobile tasks, and technology characteristics will be critical for wireless interface design. Future research in these areas is needed to improve the usability of mobile commerce.