This paper uses case study methodology to examine the phenomena of uncontrolled or informal communication (rumours) in an organization in the process of planned change accompanying the implementation of an enterprise resource planning system (ERP). This case study shows the effects of staff resistance, and detrimental rumours in particular, during the course of an information systems implementation in a large organisation. The information systems literature identifies that staff resistance to a new system implementation can influence negatively on both the course of the implementation and user uptake of the system as shown in the modified technology acceptance model (TAM). The staff perceptions in this case shows that rumours may fuel negative perceptions about the new system if not effectively managed, and result in staff displaying resistant behaviours. The findings from this study recommend that staff perceptions are monitored and appropriate management strategies employed to more effectively ameliorate uncontrolled communication in organisations adopting new technology.