The primary purpose of ISO 13304-1:2013 is to provide minimum acceptable criteria required to establish procedure of retrospective dosimetry by electron paramagnetic resonance spectroscopy and to report the results. The second purpose is to facilitate the comparison of measurements related to absorbed dose estimation obtained in different laboratories. ISO 13304-1:2013 covers the determination of absorbed dose in the measured material. It does not cover the calculation of dose to organs or to the body. It covers measurements in both biological and inanimate samples, and specifically: based on inanimate environmental materials, usually made at X-band microwave frequencies (8 GHz to 12 GHz); in vitro tooth enamel using concentrated enamel in a sample tube, usually employing X-band frequency, but higher frequencies are also being considered; in vivo tooth dosimetry, currently using L-band (1 GHz to 2 GHz), but higher frequencies are also being considered; in vitro nail dosimetry using nail clippings measured principally at X-band, but higher frequencies are also being considered; in vivo nail dosimetry with the measurements made at X-band on the intact finger or toe; in vitro measurements of bone, usually employing X-band frequency, but higher frequencies are also being considered. For the biological samples, the in vitro measurements are carried out in samples after their removal from the person and under laboratory conditions, whereas the measurements in vivo may take place under field conditions. NOTE The dose referred to in ISO 13304-1:2013 is the absorbed dose of ionizing radiation in the measured materials.