[en] The seeds of the rice variety 'Guanglu No.4' were treated by the ¹³⁷Cs and ⁶⁰Co gamma-rays. It was found that the effect of ¹³⁷Cs on the mutation on heading stage and the plant height in M₂ generation were similar to that of ⁶⁰Co. The mutation frequency was increased with increasing the dose when the dose was lower than 40 kR. The maximum mutation frequency on heading stage induced by ¹³⁷Cs and ⁶⁰Co observed at the 50 kR/min, and the maximum mutation frequency on plant height induced by the two radiation sources was at the 100 R/min and 50 R/min respectively