A new type of opto‐optical modulation effect in nematic liquid crystals is experimentally observed. The transmitted intensity of a He‐Ne laser beam passing through a liquid crystal sample while applying a dc voltage is modulated by illuminating the sample with a xenon flash lamp pulse. The response time is fast, of the order of several milliseconds. The modulated state lasts for about 500 ms. A modulated intensity of light as large as ten times the unmodulated one is obtained. The physical origin of this effect is also discussed.