The relative quantum yield of spectral sensitization (ø_r) is given by the ratio of the quantum yield of latent-image formation upon excitation of sensitizing dyes to that upon excitation of silver halide grains, being regarded as the quantum yield of the light-induced electron transfer from sensitizing dyes to silver halide grains (ø_s) under the assumption that the behavior of positive holes is independent of whether they are created by the excitation of sensitizingdyes or by the excitation of silver halide grains. We point out, however, that in some special cases ø_r is not equal to ø_s, sincethe behavior of positive holes created in sensitizing dyes is different from that of positive holes created in silver halides. The conditionis described for the measurement of ø_r that is equal to ø_s.