  We consider the bounds for the values of higgs mass $M_H$ and of the mass of
the extra quarks and leptons $M_{extra}$ derived from the stability of vacuum
and from the absence of Landau pole in Higgs potential. We find that in the
case of the absence of new physics up to the GUT scale the bounds for the mass
of the 4th generation are so restrictive that the negative result of CDF search
for extra quarks closes the window for fourth generation. In the case of the
absence of new physics up to $10^5$ GeV we get weaker but still nontrivial
bounds on $M_H$ and $M_{extra}$ as well.
