  We examine the energetics of Coronal Mass Ejections (CMEs) with data from the
LASCO coronagraphs on SOHO. The LASCO observations provide fairly direct
measurements of the mass, velocity and dimensions of CMEs. Using these basic
measurements, we determine the potential and kinetic energies and their
evolution for several CMEs that exhibit a flux-rope morphology. Assuming flux
conservation, we use observations of the magnetic flux in a variety of magnetic
clouds near the Earth to determine the magnetic flux and magnetic energy in
CMEs near the Sun. We find that the potential and kinetic energies increase at
the expense of the magnetic energy as the CME moves out, keeping the total
energy roughly constant. This demonstrates that flux rope CMEs are magnetically
driven. Furthermore, since their total energy is constant, the flux rope parts
of the CMEs can be considered to be a closed system above $\sim$ 2 $R_{\sun}$.
