Martin Hairer Exponential Mixing Properties of Stochastic PDEs Through Asymptotic Coupling (315K, Postscript) ABSTRACT. We consider parabolic stochastic partial differential equations driven by white noise in time. We prove exponential convergence of the transition probabilities towards a unique invariant measure under suitable conditions. These conditions amount essentially to the fact that the equation transmits the noise to all its determining modes. Several examples are investigated, including some where the noise does {\it not} act on every determining mode directly.