The genome projects – from microorganisms to vertebrates and mammals – create huge amounts of undeciphered genetic information. This cumulated DNA sequence bank needs intelligent, but as simple as possible, model systems to turn the currency of genomics into functional genomics. Only in one vertebrate, the mouse, it has been feasible to carry out genetic engingeering with the precision of homologous recombinantaion for over a decade. Germ line competent zebrafish ES cell lines, which can be genetically modified in vitro through homologous recombination, have an almost completed zebrafish genome sequence and microarray technology, zebrafish is in the frontier as model species in functional genomics. This development offers aquaculture a model species w hich can (and should) be used for research from quality studies of gene-function relationships in teleost fish to gain a deeper understanding of the complex traits in commercially important marine species. As active participant in this technology develop ment, Alestrom Zebrafish Laboratory at the Norwegian School of Veterinary Scinece now is able to establish the knockout zebrafish model (KO-ZFISH).