The aging of SRC-II heavy distillate has been studied under oxygen or nitrogen atmospheres at a temperature of 60℃ for one month. IR spectra, viscosities, calorific values, and elemental analyses have been determined to characterize the aging behavior of samples. The oxygen aged samples exhibit a new IR band at 1700^-1cm which is not shown in the nitrogen aged samples. The viscosity increases by 325% in oxygen, but only 18% in nitrogen, after one month of aging at 60℃. The sample aged in oxygen for on month shows a significant decrease in the heat of combustion, 106cal/g. On the other hand, the decrease for the nitrogen aged sample is only 13cal/g. Elemental analyses show that the content of carbon decreased by 1.03wt% and that of hydrogen by 0.2wt% in the oxygen aged sample compared with the unaged sample. No significant change occurs in the nitrogen aged sample. An examination has been made of the extent to which the experimental values of combustion heat can be fitted by various literature equations relating heats of combustion of coals to the elemental analyses. It is found that the equation of Mott and Spooner gives good absolute agreement(within 0.47% err) with our experimental values.