Collaboration is a growing practice among agencies, between government staff and citizens, among citizens in neighbourhoods, in environmental problem-solving and many other planning-related tasks. Although only a fraction of these efforts have been documented, there is considerable evidence that such processes can not only break through stalemates, but also produce creative solutions to complex and controversial problems and win the support and cooperation from many players that is necessary for action and results. While collaboration is not a panacea, research suggests it is underutilised for many situations. Bureaucrats, elected officials and planners themselves often stand in the way of collaboration, preferring to keep control, without recognising how collaboration can reduce conflict, prevent mistakes, enrich their thinking, offer new options and reframe difficult problems. Such desirable results are contingent, however, on properly designed and managed processes that approximate the ideal of collaborative rationality. My colleagues and I developed this model on the basis of decades of research on collaborative stakeholder processes and their outcomes. This essay outlines the basic features of collaborative rationality and discusses how planners in real situations can conduct this type of practice.