Towards a new kilogram definition based on a fundamental constant

The further development of the International System of Units and the redefinition of the mass unit based on a fundamental constant is a priority task of the metrology community. Two main strategies are pursued today, counting atoms and relating mechanical to electrical power. In this article the actual status of the kilogram and the different proposed methods are reviewed. To cite this article: W. Schwitz et al., C. R. Physique 5 (2004).