Experiments were performed to study the protective property of 5 × 10−2M cysteine and 2 × 10−3M glutathione against radiation induced chromosome damage in the root tips ofHordeum vulgare.The protective ability was examined by scorings in anaphase cells 24 hours after 200, 400 and 600r of X-irradiation. It was found that cysteine showed a more significant level of protection against radiation induced chromosome fragments, fragments and bridges or bridges than did glutathione.