Abstract. Stochastic Galerkin finite element approximation of PDEs with random inputs leads to linear systems of equations with coefficient matrices that have a characteristic Kronecker product structure. By reformulating the systems as multi-term linear matrix equations, we develop an efficient solution algorithm which generalizes ideas from rational Krylov subspace approximation. The new approach determines a low-rank approximation to the solution matrix by performing a projection onto a low-dimensional space and provides an efficient solution strategy whose convergence rate is independent of the spatial approximation. Moreover, it requires far less memory than the standard preconditioned conjugate gradient method applied to the Kronecker formulation of the linear systems.Key words. generalized matrix equations, PDEs with random data, stochastic finite elements, iterative solvers, rational Krylov subspace methods.AMS subject classifications. 35R60 , 60H35, 65N30, 65F101. Introduction. This paper is concerned with the design and implementation of efficient iterative solution algorithms for high-dimensional linear algebra systems that arise from Galerkin approximation of elliptic PDE problems with correlated random inputs. The tensor product structure of the Galerkin approximation space and the low-rank structure that is inherent in the discrete systems is exploited in our innovative solution strategy. This strategy builds on recent progress in rational Krylov subspace approximation (see, for example, Simoncini [21]) and generates an accurate reduced basis approximation of the spatial component of the Galerkin solution.We focus on stochastic steady-state diffusion equations with homogeneous Dirichlet boundary conditions. To this end, let D ⊂ R 2 be a sufficiently regular spatial domain and let Ω be a sample space associated with a probability space (Ω, F , P). Our goal is to approximate u : D × Ω → R such that P-a.s.,