We studied the pump intensity dependence of the 2WM gain in a photorefractive GaAs:EL2 crystal, with a 3.3 kV/cm d.c. field, at two different wavelengths. The grating period was 37 Am and the beam ratio was 4. At 1.32 μm, the characteristics exhibits a resonant behaviour (with a maximum of 0.23 cm-1). As for InP:Fe, these results can be explained by considering that thermally and optically generated carriers are of different types. The curve at 1.047 Am exhibits an original feature. At low intensities the gain as the same sign than at 1.32 μm (with a maximum of 0.12 cm-1), but the sign changes with increasing intensity and the gain tends towards an asymptotic value of -0.15 cm-1. Such behaviour may also be explained with the same model.