Mass Profiles of Galaxy Clusters from the Projected Phase-space Distribution of Cluster Members

I review our current knowledge of the mass distribution in clusters, as obtained from the analysis of the projected phase-space distribution of cluster galaxies. I discuss the methods of analysis, their relative advantages and disadvantages, and their reliabilities. I summarize the most recent and important results on the mass distributions of galaxy systems, from nearby to medium-distant systems, and from groups to clusters. In particular I consider how well different proposed models fit the observed cluster mass distribution, and which are the relative distributions of galaxies, baryons, and dark or total mass in clusters. I also discuss the current observational evidence for mass accretion onto galaxy systems, coming mostly from the analysis of the velocity anisotropy profiles.