  We re-examine the method of deprojection of proper motions, which has been
used for finding the velocity ellipsoid of stars in the nearby Galaxy. This
method is only legitimate if the lines of sight to the individual stars are
uncorrelated with the stars' velocities. Very simple models are used to show
that spurious results similar to ones recently reported are obtained when
velocity dispersion decreases with galactocentric radius in the expected way. A
scheme that compensates for this bias is proposed.
