  In a recent paper, Barrera and Fuchs [Phys. Rev. B 52, 3256 (1995)] provide a
theory of electron energy loss in a random system of spheres. In this comment,
we point out that the approach of Barrera and Fuchs (A) completely ignores
magnetic excitations and retardation, which is inconsistent with the data of
energy loss of fast electrons, (B) does not yield the correct k-->0 limit,
hence, does not recover correctly the Maxwell-Garnett formula, and (C) does not
use the correct screened potential at any k.
