Estimates show that knowledge workers perform approximately 50 percent of their workplace tasks while they are on the go. Mobile workers frequently require access to task-relevant instruction or knowledge in remote work environments where desktop or even laptop computers are impractical. Recently there has been a convergence of enabling technologies and an increased interest in the use of mobile devices, such as Smart Phones and Personal Digital Assistants (PDAs), to support worker learning and performance. This is evidenced by the popularity of Web sites (e.g., mLearnopedia.com) and journals (e.g., International Journal of Interactive Mobile Technologies) dedicated to mobile learning (mLearning) and mobile performance support (mSupport). Most of this interest has been focused on mLearning rather than mSupport, and there is a tendency to assume that what works in practice for mLeaning will work for mSupport. This assumption may not be tenable. Therefore, there is a need for the educational community to better understand mLearning and mSupport, as well as the characteristics of mobile devices, their users, and their operational environments, to maximize the educational value of mobile devices for mSupport. We provide a discussion of mLearning and mSupport that focuses on six user-centered issues likely to determine mobile device effectiveness and user acceptance for mSupport: 1) device characteristics, 2) form factor, 3) user interaction styles, 4) task characteristics, 5) content management, and 6) context awareness. We examine these issues and discuss potential solutions. In addition we provide real-world context via a hypothetical scenario from the hazardous materials transportation domain.