We have investigated the importance of the form of the driving mechanism in MHD simulations of coronal mass ejections. Previous authors have performed simulations using a thermal driving mechanism, and have found that this mechanism cannot reproduce the observed features of mass ejections unless an elaborate model of the initial corona is used. We have devised a model simulation problem and have found that the use of a simple form for the initial corona, with an upward moving parcel of cold, dense plasma as the driving mechanism, can produce results that are consistent with many of the features observed by coronagraphs. Our results imply that the nature of the driving mechanism may play an important role in determining the dynamical evolution of mass ejections. ¿ American Geophysical Union 1990