A simple model of an axisymmetric tandem mirror is employed to study the stability of global (low‐m) ballooning modes in the central cell. The presence of a perfectly conducting wall in the model gives an estimate of the effect of wall stabilization. The scaling of the critical &bgr; ( = 2p/B2) with mode numberm, connection lengthLcto the end plug, and wall positionwis computed for several magnetic field profiles.