AOM and lamp tests were carried out with soybean, corn, palm oil and beef tallow without the addition of antioxidant. The evaluation of rancidity for the stability was determined by changes of peroxide value and acid value, and the correlation between the stability and the composition of fats and oils was examined. The results obtained were as follows. 1. In the AOM test, POV began to rise in the order of corn oil, soybean oil, beef tallow and palm oil. However, the time required to reach POV 100 in beef tallow was faster than other fats and oils. It was found that there was a good correlation between POV and content of tocophrol. 2. In the lamp test by light of main wavelength 253.7nm, beef tallow was stabler than soybean and corn oil. It was because the absorption of light into beef tallow was much smaller than others, since beef tallow was fats. Palm oil was very stable in all the samples during AOM and lamp test.