An information system delivers support for decision making; however the physical constraints associated with mobile work often means that such support is limited. Despite the limitations, mobile workers manage to get work done. A broader review of a mobile worker’s information system use reveals information sources that are outside the usual analysis of the technology and data. Decision making in mobile work would benefit from the development of these alternative information sources. A comprehensive description of the existing information system of mobile workers is a vital step in supporting technology development. This paper considers two different mobile workers, their information system and how they interact with that system. To assist in presenting a holistic view of the case studies, Activity Theory is used as a lens of interpretation.