  The mass distribution of galaxy clusters can be determined from the study of
the projected phase-space distribution of cluster galaxies. The main advantage
of this method as compared to others, is that it allows determination of
cluster mass profiles out to very large radii. Here I review recent analyses
and results on this topic. In particular, I briefly describe the Jeans and
Caustic methods, and the problems one has to face in applying these methods to
galaxy systems. Then, I summarize the most recent and important results on the
mass distributions of galaxy groups, clusters, and superclusters. Additional
covered topics are the relative distributions of the dark and baryonic
components, and the orbits of galaxies in clusters.
