It is generally accepted that the first compounds formed by oxidation of an oil are hydroperoxides. The usual method of hydroperoxide assessment is by determination of the Peroxide Value, which is reported in units of millimole of hydroperoxide per kilogram of oil (or expressed as milliequivalents of iodine per kilo of oil). The peroxide value is an indicator of the products of primary oxidation. It measures rancidity or degree of oxidation, but not stability of an oil.