Snapdragon (Antirrhinum majus L.) is one of the principal cut-flower crops grown in many parts of the world, in favorite environment, as in the winter season in Egypt. The plant is a popular winter annual propagating by seeds, The plant is characterized with magnificent flowers that are borne on terminal long spikes of many colours and numerous shades. A. majus is considered as the most important species among about 32 other species belonging to the genus Antirrhinum, tribe Antirrhineae, sub-family Antirrhinodeae, family Scrophulariceae In the present study; the precise effect of ionizing radiation, especially gamma rays, on three snapdragon (Antirrhinum majus, L.) varieties was evaluated, in an attempt to establish the suitable conditions for mutation breeding of this important ornamental crop plant.