  Current data point toward metastability of the electroweak vacuum within the
Standard Model. We study the possibility of stabilizing the Higgs potential in
U(1) extensions thereof. A generic Z$'$ boson improves stability of the scalar
potential in two ways: it increases the Higgs self--coupling, due to a positive
contribution to the beta--function of the latter, and it decreases the top
quark Yukawa coupling, which again has a stabilizing effect. We determine the
range of U(1) charges which leads to a stable electroweak vacuum. In certain
classes of models, such stabilization is possible even if the Z$'$ does not
couple to the Higgs and is due entirely to the reduction of the top Yukawa
coupling. We also study the effect of the kinetic mixing between the extra U(1)
and hypercharge gauge fields.
