Abstract: The basic structure of mature chloroplasts of leaves of the wild rice (Oryza sativa L. f. spontanca) was found to be similar to that of cultivated rice Oryza saliva L. ). The chloroplasts of cultivated rice had more grana, more grana lamellae and showed greater electron density of the cytoplasm than those of the wild rice species.The chloroplasts of wild rice had more stroma lamellae and more osmiophilic bodies than those of the cultivated rice.The chloroplasts of cultivated rice which contained a number of starch granules were adjacent to mitochondria and peroxisomes. Starch granules were observed in the chloroplast of annual wild rice, but not in the perennial wild rice. These results support the theory that the rice line of Southern China might have originated from O. sativa L. f. spontanca and showed that the cultivated rice was more closely relation to the annual wild rice than to the perennial wild rice.