This International Standard provides recommendations for dealing with discrepancies between dosimeter systems used in parallel, in order to comply with established criteria and national regulations. This International Standard gives guidelines for investigating and analysing the discrepancies between the results of personal dosimetry systems, using two or more dosimeters (often one passive dosimeter and one active dosimeter), worn in parallel by the same worker. This International Standard identifies when the difference between measurements made by personal dosimetry systems used in parallel is considered significant and, hence, needs to be investigated. It specifies the treatment of this difference. In this International Standard, only the personal dose equivalent, Hp(10), from photon radiation is considered. Exposure to beta particles and neutrons might need to be taken into account when identified discrepancies are investigated. This International Standard applies to situations where the period of wearing can be integrated to the same period of time for both systems.