Zebrafish research has already yielded important insights into vertebrate development and human disease, and might now be able to add liver disease to its list of achievements. On p. 3561, Sadler et al. describe how they screened 297 zebrafish lines carrying mutations in genes essential for embryonic development for an enlarged liver (hepatomegaly),which is a sign of many liver disorders. From this screen, they identified seven mutants with hepatomegaly, three of which (vps18, nf2 and foie gras) have phenotypes resembling human liver diseases, namely human arthrogryposis-renal dysfunction-cholestasis syndrome (vps18),choledochal cyst formation (nf2) and fatty liver disease (foie gras). These mutants should provide valuable models for the future study of liver development, and for the investigation of the molecular pathogenesis of congentital biliary disorders and of the common human disorder fatty liver disease.