  We review our current understanding of the internal dynamical properties of
the dwarf spheroidal galaxies surrounding the Milky Way. These are the most
dark matter dominated galaxies, and as such may be considered ideal
laboratories to test the current concordance cosmological model, and in
particular provide constraints on the nature of the dominant form of dark
matter. We discuss the latest observations of the kinematics of stars in these
systems, and how these may be used to derive their mass distribution. We tour
through the various dynamical techniques used, with emphasis on the
complementarity and limitations, and discuss what the results imply also in the
context of cosmological models. Finally we provide an outlook on exciting
developments in this field.
