Abstract: The upper limit of acid value of rice bran oil, after naturally stored as rice bran and as the oil for 1 to 2 years, has been discussed statistically. The average properties of rice bran sample were 12.6% in moisture and 18.9% in oil content.From the above result, natural hydrolysis will not be suitable to prepare crude fatty acid for distillation because of low degree in the hydrolysis. There was about 2% decrease of fatty material in the rice bran when naturally hydrolysed. The higher acid value of oil in the rice bran showed a decreased remaining oil content in the extracted flakes, indicating the influence of natural hydrolysis. Also, the acid value of remained oil in the extracted flakes was lower than that of raw rice bran. From these results, it is presumable that the fatty acid is solvent-extracted easier than the glycerides and esters.