Bricmont J. , Kupiainen A. High Temperature Expansions and Dynamical Systems (87K, Latex) ABSTRACT. We develop a resummed high-temperature expansion for lattice spin systems with long range interactions, in models where the free energy is not, in general, analytic. We establish uniqueness of the Gibbs state and exponential decay of the correlation functions. Then, we apply this expansion to the Perron-Frobenius operator of weakly coupled map lattices.