The pulse response of the linear electro-optic effect is investigated with high temporal and spatial resolution in KDP, KD*P, and biaxial LiCOOH H,O. Experimental results, which are explained theoretically, show that the piezo-optic transients induced by the piezoelectric effect, are generated by stress release waves. Starting from the surfaces, these excite by reflection, diffraction, and superposition, due to the finite crystal dimensions, normal vibration modes too. It is shown that the direct electro-optic effect can be measured for all crystal classes a t the beginning of the pulse response. The pulse method also yields static electro-optic, piezo-optic, and elastic constants. The values of ri3, r63, p6, and cs6 mensured in KDP, agree well with those of other authors. Measurement of the direct electrooptic effect of LiCOOH H,O in some directions yields values within 1 to 4 x m/V.