Tracing the Cluster Internal Dynamics with Member Galaxies

The analysis of the spatial distribution and kinematics of galaxies in clusters allows one to determine the cluster internal dynamics. In this paper, I review the state of the art of this topic. In particular, I summarize what we have learned so far about galaxy orbits in clusters, and about the cluster mass distribution. I then compare four methods that have recently been used in the literature, by applying them to the same data-set. The results stress the importance of reducing systematic besides random errors, for a reliable determination of cluster mass profiles.