TITLE: On the Use of Open Boumdary Conditions in Block Gauss-Seidel Methods for the Convection-Diffusion Equation Author: F. Nataf e-mail: nataf@cmapx.polytechnique.fr Preprint n 283 In the context of convection-diffusion equation, we consider the use of open boundary conditions (also called radiation boundary conditons, absorbing B.C.) in Block Gauss-Seidel algorithms. Theoretical results and numerical tests show that the convergence is thus accelerated. The whole paper is available as a compressed Postscript file by internet procedure FTP anonymous on host barbes.polytechnique.fr ( 129.104.4.100) in the directory pub/RI/1993 under the name nataf.283.nov.93.ps.gz