Oxidation of hexadecane under y-irradiation has been studied. The major product is a peroxide. With a dose rate at 940 cad per minute, a P value of 340 and G value of 490 were obtained, indicating a chain reaction mechanism. The yield of peroxide from irradiation (2 to 11 hours) at 90-1350 was investigated. When oxidation was carried out at 1200 for 7 hours, the yield of peroxide reached 9% based on hexadecane. The method of separation of the peroxide from the oxidation mixture has also been investigated. High vacuum distillation (10-5 mm) and aluminium oxide column chroma-tography were tried; the latter was found to be superior. A concentration of peroxide with 98% purity could easily be obtained. Elementary analyses, molecular weight determination, and infra-red absorption spectral measurement all indicated that the peroxide obtained from the above oxidation was a hexadecane hydroperoxide.