The collapse of pure vapor bubbles in an infinite liquid initially perturbed from a spherical shape is simulated numerically for two cases. In Case A the bubble is initially close to a prolate ellipsoid, and in Case B it is initially close to an oblate ellipsoid. Nonlinear effects are determined by comparing the results with those predicted by the linearized theory of Plesset and Mitchell. These nonlinear effects are found to be important only in the final stages of collapse. In Case A a pair of inward moving jets develop and strike each other with a final speed which is roughly half that, predicted from the linear theory.