  We discuss recent measurements of proper motions of the hotspots of Compact
Symmetric Objects. Source expansion has been detected in ten CSOs so far and
all these objects are very young (<3000 years). In a few sources ages have also
been estimated from energy supply and spectral ageing arguments and these
estimates are comparable. This argues that these sources are close to
equipartition and that standard spectral ageing models apply. Proper motions
studies are now constraining hotspot accelerations, side-to-side motions and
differences in hotspot advance speeds between the two hotspots within sources.
Although most CSOs are young sources their evolution is unclear. There is
increasing evidence that in some objects the CSO structure represents a new
phase of activity within a recurrent source.
