The stability of axisymmetric modes is studied by using the general ideal-MHD code ERATO. The parameters investigated are the triangularity and the elongation of the tokamak meridian cross-section and the distance between the plasma and an external conducting wall. Both aspect ratio, R/a = 3, and safety factor on the axis, q0 = 1, are kept fixed. The validity of simpler models is tested. Wall stabilization is found to be effective for axisymmetric modes.