Book excerpt: ICRP Publication 74 provides an extensive and authoritative set of data linking the operational quantities defined by ICRU with the dosimetric and protection quantities defined by ICRP. The operational quantities provide a satisfactory basis for most of the measurements for radiation protection against external radiations. In those cases where it is not so, the data given in the report provides a basis for designing special measurement programmes, properly interpreting their results and relating them to the protection quantities. The report should be useful to operational health physicists, medical physicists and those involved in the calibration of instruments and personal dosimetry.