2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/3448The 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.12 pages, 8 figures, invited review at the workshop "Tracing Cosmic Evolution with Galaxy Clusters" (Sesto 2001), ASP Conference SeriesAstrophysicstext