A simple method was used to determine the "effective" penetration depth of backscattered electrons. The technique was to examine electron channeling patterns (ECPs) of Si〈100〉 single crystals, covered by different thicknesses of polycrystalline aluminum layers. The "effective" depth was established as a function of electron energy. It was determined that this depth differs from that anticipated by theory but is consistent with other experimental data. Some reasons for this discrepancy are discussed.