Proper motions for K and M giants in the bulge of the Milky Way were measured through Baade's window. The proper motions are of sufficient precision for velocity dispersions to be determined. For the entire sample, the motions appear to be very nearly isotropic, with the dispersion in one coordinate just over 100 km/s (for a distance of 7.7 kpc). There is some indication that the more metal-rich stars have a larger dispersion in Galactic longitude than in Galactic latitude, although this awaits confirmation with a larger sample.
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Spaenhauer et al. (1992) studied this question.