A field experiment was carried out at ACSAD research station in deirezzor district during two seasons 1987/88 and 1988/89 on medium heavy textured soil. The aim was to study the effects of five doses of gamma rays 0, 5, 10 and 20 Gy and four levels of nitrogen 0, 50, 80 and 100 Kg N/ha, and the interaction effect on barley`s yield (c-v arabic abiad) under irrigated conditions. The results showed that the irradiation doses and nitrogen rates significantly increased barley`s grain and straw yield compared to control. The doses 5, 10, 15 and 20 Gy increased grain yield by 28.3, 25.4, and 19.9% and straw yield by 14.2, 7.0, 8,9 and 0.9% respectively. While nitrogen levels 50, 80 and 100 Kg N.ha lead to grain yield increases by 24.8, 32.0, and 29,9% and straw yield increases 19.2, 17.0 and 3.1% respectively. The highest positive interaction was observed at 50 Kg N/ha and doses 5 and 20 Gy. In general, the increase in radiation doses and nitrogen levels lead to a drop in the yield. 7 tabs.