In this paper we review the Rebuilding Macroeconomic Theory Project, in which we asked a number of leading macroeconomists to describe how the benchmark New Keynesian model might be rebuilt, in the wake of the 2008 crisis. The need to change macroeconomic theory is similar to the situation in the 1930s, at the time of the Great Depression, and in the 1970s, when inflationary pressures were unsustainable. Four main changes to the core model are recommended: to emphasize financial frictions, to place a limit on the operation of rational expectations, to include heterogeneous agents, and to devise more appropriate microfoundations. Achieving these objectives requires changes to all of the behavioural equations in the model governing consumption, investment, and price setting, and also the insertion of a wedge between the interest rate set by policy-makers and that facing consumers and investors. In our view, the result will not be a paradigm shift, but an evolution towards a more pluralist discipline.