SUMMARYIn this paper, we study a multigrid (MG) method for the solution of a linear one-dimensional convectiondi usion equation that is discretized by a discontinuous Galerkin method. In particular we study the convection-dominated case when the perturbation parameter, i.e. the inverse cell-Reynolds-number, is smaller than the ÿnest mesh size.We show that, if the di usion term is discretized by the non-symmetric interior penalty method (NIPG) with feasible penalty term, multigrid is su cient to solve the convection-di usion or the convection-dominated equation. Then, independent of the mesh-size, simple MG cycles with symmetric Gauss-Seidel smoothing give an error reduction factor of 0.2-0.3 per iteration sweep.Without penalty term, for the Baumann-Oden (BO) method we ÿnd that only a robust (i.e. cellReynolds-number uniform) two-level error-reduction factor (0.4) is found if the point-wise block-Jacobi smoother is used.