Astronomical Institute, Prague
New determination of the Earth orientation parameters, based on optical astrometry observations since the beginning of the century, is now under preparation by the working group established by Commission 19 of the IAU. The Hipparcos catalog is to define the celestial reference frame in which the new series of EOP are to be described. The novelties of the prepared solution are the higher resolution (5 days) and more parameters to be estimated from the solution (e.g., celestial pole offsets, rheological parameters of the Earth, certain instrumental constants or systematic seasonal deviations of individual instruments). Mathematical model of the solution will be described, and preliminary results based on observations made with more than fourty instruments will be presented and analyzed.