FRAS is a system that, with the use of the d-ROMs test Diacron kit, gives the measurement of "Reactive Oxygen Metabolites," exactly as the d-ROMs says in it's name (Reactive Oxygen Metabolites). Free Radicals have a very short half-life, they are unstable and they only react locally where they are produced, so therefore, measurement in clinical diagnosis is not possible. We do not exactly measure free radicals with FRAS, but we measure the products of oxidation that the free radicals have generated in the cell, oxidating lipids, proteins, amminoacids etc. These products (hydroperoxides) are expelled from the cell, enter the blood flow, are stable and are proportional to the number of free radicals that generated them. When we put the drop of blood into contact with the reagent, we transform the hydroperoxides into free radicals again and they remain trapped and redden the reagent itself. The intensity of the colour is proportional to the quantity of free radicals present. The photometer transforms the intensity of the colour into a value which is expressed in Carr Units. The Carr Unit is the unit that gives oxidative stress measurement. Normal values are below 250 U Carr; border line values are between 250 and 300; oxidative stress values are between 300 and 400; and strong oxidative stress values are over 400. Therefore, with FRAS it is possible to measure all the hydroperoxides that are present in the blood and consequently have oxidative stress values with a simple, reliable, reproduceable, fast and non-expensive method. FRAS has been validated by the CNR (National Research Council), it is used by various Research Centres and Universities; it has been quoted in numerous publications in Italy and abroad and many others are under way. The method is based upon metals transition capacity to catalize, once these metals are freed from their chelate protein transport forms and the deposit where they are normally found in plasma and cells, reactions from the formations of free radicals according to Fenton's reaction: H2O2 + Fe2++ Fe3+ + OH• + OH- or radical propagation as follows: The radicals which are produced, whose quantity is directly proportional to the quantity of peroxide present in plasma, are chemically trapped by phenolic derivate molecules as follows: which transforms them into ions and which become radicals giving them a colouring which can be measured photometrically. Results are expressed in conventional units (Carr. unity) and 1 U.Carr. is equal to a hydrogen peroxide concentration of 0,08 mg%.