AbstractØkland, J-M., Haaland, Ø. A., and Skaug, H. J. 2010. A method for defining management units based on genetically determined close relatives. – ICES Journal of Marine Science, 67: 551–558. We propose a new method for identifying management units from genetic samples (DNA profiles). The main idea is to look at the geographic distribution of genetically determined close relatives and to use these to separate different breeding populations. The method has the potential to detect population structure emerging on a demographic time-scale, as opposed to classical population genetic methods. It is not required that the breeding populations have different allele frequencies. Using simulated datasets, the proposed method has good statistical properties throughout the range of migration rates considered. This may be a powerful method for setting management boundaries.