All advanced oxidation processes (AOP) are characterised by a common chemical feature: the capability of exploiting the high reactivity of HO radicals in driving oxidation processes which are suitable for achieving the complete abatement and through mineralization of even less reactive pollutants. The different AOP are considered and critically presented according to their specific features with reference, whenever possible, to their real applications for water pollution abatement. The experimental apparatus and working procedures which can be adopted for carrying out waste water treatments by AOP application are examined. Some remarks upon treatment economics are provided on the basis of the main parameters affecting the AOP costs.