The ability of photoinduced surface-relief-grating (SRG) formation of 4-[bis(4-methylphenyl)amino]azobenzene (BMAB) was found to be drastically enhanced by mixing with 4,4',4 ''-tris[3-methylphenyl(phenyl)amino]triphenylamine (m-MTDATA) due to the increase in glass-transition temperature (T-g). The resulting SRG inscribed on the mixed amorphous film remained even after annealing at 55 degrees C, which was considerably higher than the T-g of BMAB. These results suggest that the m-MTDATA molecules in the mixed film were transported together with BMAB molecules upon irradiation with the writing beams.