  We have performed VLT spectroscopy of an almost complete sample of 18
early-type galaxies with 0.88 < z < 1.3 plus two at z=0.67, selected from the
K20 survey, and derived the velocity dispersion for 15+2 of them. By combining
these data with HST and VLT images, we study the Fundamental Plane (FP), the
Faber-Jackson and the Kormendy relations at z~1, and compare them with the
local ones. The FP at z~1 keeps a remarkably small scatter, and shows both an
offset and a rotation, which we interpret in terms of evolution of the
mass-to-light ratio, and possibly of the size. We show evidence that the
evolution rate depends on galaxy mass, being faster for less massive galaxies.
We discuss the possible factors driving the evolution of spheroids and compare
our results with the predictions of the hierachical models of galaxy formation.
