- The bifurcation of elastic-plastic spherical shells subject to internal pressure loading is investigated. Two cases are considered; in one case, the pressure is prescribed, while in the other, the change in volume enclosed by the shell is prescribed. Attention is restricted to axisymmetric bifurcations. Separation of variables is employed to introduce a complete set of bifurcation modes. For one of these modes a simple approximate bifurcation criterion is obtained. A numerical method is then employed to investigate the bifurcation of elastic-plastic spherical shells in a variety of modes. A comparison is made between the numerical results and the predictions of the approximate criterion. Of particular interest is whether bifurcation can occur prior to the maximum pressure point. The numerical results obtained here show that this does not occur for the axisymmetric modes considered. 1975.