Global and local bias in the FK5 from the Hipparcos data

Extensive analyses of the FK5 Catalogue with respect to the Hipparcos refer ence frame have been made in order to determine the overall and local corre ctions to be applied to any FK5-based secondary frame. The global rotation in position and proper motion is significant, and for the latter, interpret ed in term of lack of inertiality of the FK5 frame and compared to a simila r analysis carried out with the PPM proper motions. Zonal corrections are l arge compared to the random errors and difficult to represent with a small number of spherical functions. The differences (including the global rotati on) are then given in the form of easy-to-use tables.