Petkus winter rye seed was subjected to ultrasonic vibrations of i Mcyc./sec. frequency in order to test the possibility of their having a vernalizing action. Seed which had not been soaked, fully imbibed seed, germinating seed (radicle showing) and seedlings with about 2 mm. long coleoptiles were treated with two intensities of ultrasonics for two periods of exposure.There is a slight favourable effect on germination rate of the unsoaked seed, but injury or death is caused by higher doses applied to the imbibed or germinated seed. Time to flowering was not affected by this treatment and no vernalization resulted.