In 1977, the International Commission on Radiological Protection issued ICRP Publication 27, “Problems Involved in Developing an Index of Harm”. That report discussed the difficulties of making an appropriate comparison of radiation and other effects and suggested a quantitative index to take account of the length of life or full activity lost as a result of occupational causes. This new report substantially extends the scope of ICRP Publication 27, by including new data on occupational accident risks as well as a consideration of radiation induced non-fatal cancers, non-stochastic effects and hereditary detriment. An appendix discussing assessments of detriment in sections of the general public due to exposure to ionising radiation is also included.