Photoreflectance (PR) and electroreflectance (ER) responses were compared on samples of GaAs in order to establish a detailed relation between the two techniques. The majority of experiments were made on an n-GaAs Schottky Barrier in the vicinity of the fundamental edge (1.4 eV). PR spectra were studied as a function of DC bias with the modulation obtained by chopped laser radiation. A complementary set of ER measurements were made over the same bias range, and a comparison was made of ER response with and without CW laser illumination. This yielded a direct relationship between CW laser power and an equivalent effective bias representing the laser irradiation reduction of the band bending. The correspon-dence between ER and PR allowed us to calculate the average electric field in the depletion layer based on the Franz-Keldysh oscillations present in both spectra. Aspnes and Studna (1973) have shown that the slope of the plot of the energy value of the oscillation extremum index n yields the average electric field provided that the interband effective masses are known. This result indicates that PR can determine submerged interfacial fields with-out any electrical contact to the sample.