A key comparison has been made between the air-kerma standards of the NIM and the BIPM in the low-energy x-ray range. The results show the standards to be in agreement at the level of the combined standard uncertainty of 3.7 parts in 10 3 . The results are analysed and presented in terms of degrees of equivalence, suitable for entry in the BIPM key comparison database. KEY WORDS FOR SEARCH Radiation dosimetry, key comparison, low-energy x-rays, air kerma Main text To reach the main text of this paper, click on Final Report . Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/ . The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).