The accumulation of a charge on the order of 10(11) e/cm-2 has been ob
served on the sur-face of porous silicon during illumination at photon
energies of 1.2-5 eV. A study was made of the kinetics of the buildup
and drain of the photoinduced charges of both signs. A possible relat
ionship between the charging of the surface and a degradation of the l
uminescence properties of the porous silicon is discussed.