  We present a novel method to recontruct the mass distribution of galaxy
clusters from their gravitational lens effect on background galaxies. The
method is based on a least-chisquare fit of the two-dimensional gravitational
cluster potential. The method combines information from shear and magnification
by the cluster lens and is designed to easily incorporate possible additional
information. We describe the technique and demonstrate its feasibility with
simulated data. Both the cluster morphology and the total cluster mass are well
reproduced.
