  We introduce a natural definition of the renormalized volume of a
4-dimensional Ricci-flat ALE space. We then prove that the renormalized volume
is always less or equal than zero, with equality if and only if the ALE space
is isometric to its asymptotic cone. Currently the only known examples of
4-dimensional Ricci-flat ALE spaces are Kronheimer's gravitational instantons
and their quotients, which are also known to be the only possible examples of
special holonomy. We calculate the renormalized volume of these spaces in terms
of Kronheimer's period map.
