[en] The D₂O concentration of the Canadian Primary Standard has been reviewed and an accurate redetermination of the deuterium content has been made using the absolute method recently developed at CRNL. A new value of 99.9720 +- 0.0006 wt percent has been determined and its use is recommended. On and after November 1, 1984 the assigned concentration values of secondary standards based on the Canadian Primary Standard should be changed correspondingly as should the value for heavy water in reactors and inventory and the associated reactor grade specifications. The new value of the Canadian Primary Standard is in good agreement with results from international intercomparisons, is directly established with absolute determinations, and is easily verifiable in the future. An appendix describes a container which facilitates intercomparisons and long term storage of standards and their handling in interlaboratory comparisons