  We compare the 3D clustering of old passively-evolving and dusty star-forming
z~1 EROs from the K20 survey. With detailed simulations of clustering, the
comoving correlation length of dusty star-forming EROs is constrained to be
less than r_0~2.5 Mpc/h. In contrast, the old EROs are much more positively
correlated, with 5.5<~r_0/(Mpc/h)<~16, consistent with previous claims for z~1
field early-type galaxies based on analyses of ERO angular clustering. The low
level of clustering of dusty star-forming EROs does not support these to be
major mergers building up an elliptical galaxy, or typical counterparts of
SCUBA sources, but it is instead consistent with the weak clustering of high
redshift blue galaxies and of luminous local IRAS galaxies. Current
hierarchical merging models can explain the large r_0 for z~1 field early-type
galaxies, but fail in matching their high number density and overall old ages.
