The zebrafish is as a powerful vertebrate model system for modeling human disease including liver pathology. In ZFE, hepatic responses can be expected after exposure to hepatotoxicants, because hepatocytes are present from 36-hpf and at 72-hpf the liver is fully functioning. These characteristics make the whole ZFE an attractive alternative model for compound-induced hepatotoxicity screening. Therefore, the main objective of this study is to further strengthen the applicability of whole ZFE as an alternative model for hepatotoxicity testing, with a special focus on the ability to identify gene expression responses in whole ZFE that are suggestive of hepatotoxicity. Deep sequence technology is applied to assess whether hepatotoxicity-specific transcripts that are identified in livers of hepatotoxicant treated adult zebrafish can be detected in whole ZFE as well. Overall design: Whole zebrafish embryo and adult zebrafish are exposed for 48 hours to human hepatotoxicants. Afterwards, the adult liver is dissected and snap frozen untill processed for RNA isolation. The whole zebrafish embryos are pooled, one sample consists of 15 embryos, and are also snap frozen untill processed for RNA isolation. For every sample RNA is isolated according to the protocol of de Jong et al (2009). and then equal amounts of every sample is pooled. The two pools (one for the adult zebrafish liver, the other for the whole zebrafish embryo) are sequenced.