  Astrometric space missions like Gaia have stimulated a rapid advance in the
field of relativistic astrometry. Present investigations in that field aim at
accuracies significantly less than a microarcsecond. We review the present
status of relativistic astrometry. As far as the problem of light propagation
is concerned we face two problems: the form of the BCRS metric and solutions to
the light-ray equation. Finally, work in progress in that field is briefly
mentioned.
