The effect of polyamine on chlorophyll amount, chloroplast peroxidase and chloroplast thylakoid protein in rice leaf segments which were grown for 10 days(16 hrs, light : 8 hrs, dark) in a hormone-free MS medium containing polyamine was studied. Polyamine treatment increased the chlorophyll contents compared with the control in rice leaf segments. Especially spermine was most effective. Also, in rice leaf segments treated with polyamine chloroplast peroxidase activity was higher than in the control. The treatment with lmM of spermidine increased the enzyme activity by 100%. In polyamine treatment and control two major polypeptide bands corresponding to 56 and 25Kd molecular weight were clearly resolved with other minor bands by SDS-PAGE in the insoluble protein fraction. However, in these bands (56, 25Kd), the total area of protein in treating with polyamine were higher than that of the control. These results suggest that polyamine was an important factor in the chloroplast development of rice seedlings.