This chapter explores Sydney’s knowledge-based development, surveying reasons for its concentration of such development including the role of planning. Sydney’s high knowledge industry concentration is seen as the product of the city’s commercial leadership, its high share of transnational corporations associated with Sydney’s global economy role, and its high proportion of skilled immigration. Such factors have resulted in a knowledge sector that is concentrated around central and near northern Sydney, and in the formation of several distinct clusters of knowledge-based industries. Case studies of the information technology and telecommunication industry and the multimedia industry suggest that Sydney’s concentration of corporate headquarters has been a key driver of growth in these industries, while the presence of a large pool of computer-based skills has stimulated and fed multimedia development. Metropolitan planning strategies have lacked firm principles for the development of knowledge-based industries. Instead, planning for these industries focused on a series of ad hoc place-specific initiatives that have been much less significant than market forces in supporting knowledge-based development in Sydney.