  We investigate the breakdown of BCS superconductivity in {\em ultra}\/small
metallic grains as a function of particle size (characterized by the mean
spacing $d$ between discrete electronic eigenstates), and the parity ($P$ =
even/odd) of the number of electrons on the island. Assuming equally spaced
levels, we solve the parity-dependent BCS gap equation for the order parameter
$\Delta_P (d,T)$. Both the $T=0$ critical level spacing $d_{c,P} $ and the
critical temperature $T_{c,P} (d)$ at which $\Delta_P = 0$ are parity
dependent, and both are so much smaller in the odd than the even case that
these differences should be measurable in current experiments.
