Pre-print, Working paper: Abstract This article studies a new class of models which synthesize the two traditions of general equilibrium with nonclearing markets and imperfect competition on the one hand, and dynamic stochastic general equilibrium (DSGE) models on the other hand. This line of models has become a central paradigm of modern macroeconomics for at least three reasons: (a) it displays solid microeconomic foundations, (b) it is a highly synthetic theory, which combines in a unified framework general equilibrium, nonclearing markets, imperfect competition, growth theory and rational expectations, (c) it is also an empirical success, leading to substantial progress towards matching real world statistics.