For eCollaboration to be e ective, especially where it at- tempts to promote true collective decision-making, it is necessary to consider how knowledge is shared. The paper examines the knowledge sharing literature from the perspective of eCollaboration and discusses the critical challenges, principally the motivation of knowledge sources and maintenance of semantics, and describes how techniques and tech- nologies can be employed to alleviate the di culties. The paper con- cludes with an example of how such technologies are being applied for Emergency Response, to facilitate knowledge sharing both amongst the citizens and between the citizens and organisations.