A detailed study is presented of the influence of several parameters on the energy-loss probability of fast electrons (-100 keV) incident on small metallic spherical particles. We consider the collective modes of the sphe|e, including bulk-type modes which do not appear to have been considered previously in the literature. A Gaussian distribution is used to describe the electron in the plane transverse to the trajectory. We discuss the effects of the variation of several parameters -incident beam size, probe velocity, radius of the sphere, impact parameter, and the excited mode -and conclude that the absorption spectra depend critically on the geometry of the probe as the experimental data of Batson and Treacy suggest.