Two series of experimental fumigations were performed in 1959 and 1960 to evaluate the effectiveness of phosphine at various dosages for insect control in stacks of sacked rough and milled rice covered with gas-tight tarpaulins. The effect of the gas on adult and immature stages of rice weevils, Sitophilus oryzae (L.), and adult confused flour beetles Tribolium confusum Jacqueline du Val, and on germination of seed rice was observed. The gas concentration was analyzed at regular intervals complete control of adults of both species was obtained from all dosages used. Grain temperatures in the second series of test were much higher than those in the first series, and this appeared to alter the performance of the fumigant significantly. A dosage between 73 and 121 aluminum phosphide tablets per 1,000 cubic feet was required to kill 100per thousand of immature rice weevils in rough rice when the temperature averaged between 52° and 58° F. Fifty tablets per 1,000 cubic feet proved to be an ample dosage in milled rice at an average temperature between 80° and 90° F. Germination of seed rice was not affected by fumigation with any dosage or combination of dosages of phosphine that was used under the condition of this test.