  We investigate the spin-magnetism of mesoscopic metallic grains. In the
average response of an ensemble of grains there are corrections to macroscopic
behaviour due to both spectral fluctuations and electron-electron interactions.
These corrections are a non-linear function of the magnetic field. Their
temperature dependence is calculated numerically and analytically. An
experiment is proposed to measure the unknown interaction coupling constant in
the cooper channel. For a single sample the magnetization is found to fluctuate
reproducibly about the mean. These fluctuations directly probe the energy level
statistics.
