The equilibration in relativistic heavy-ion collisions for the systems
O-16 + O-16, Ca-40 + Ca-40 and La-139 + 139(La is studied with relati
vistic VUU theory. We have found that the mean field still plays an im
portant role in addition to the collision term in the equilibration pr
ocess in relativistic heavy-ion collisions at energy around 1 GeV/nucl
eon. The influence of the medium effect is studied. The light and medi
um systems do not reach complete equilibrium so that the concept based
on it is questionable at the energy domain 1 GeV/nucleon.