Genetic diversity, population structure and phylogeography of four species of Antarctic fish (Notothenioidei, Teleostei) across the Scotia Ridge shall be determined by investigating mitochondrial control region sequences, microsatellite markers, and sequences of the nuclear hemoglobine and antifreeze glycoprotein genes. The Antarctic Region fulfils most of the essential parameters of lakes containing radiations of fish and is therefore equivalent to a closed basin, providing a comparable opportunity for studying adaptive radiation within a confined area. Population genetic data are available for only a limited number of Antarctic fish species. Whether there is substantial genetic structure or not is of particular importance not only for the management of Antarctic fisheries but also for a general understanding of evolutionary pathways like the influence of geography, hydrography and reproduction mode on dispersal and speciation in the Antarctic environment.