 Zebrafish have a total of 94 cytochrome p for 50 CYP genes distributed among 18 gene families found also in mammals. These CYP genes are involved in both endogenous and exogenous chemical transformations with potential implications for normal physiology and disease processes. A particular interest are the 32 CYP genes from families 5 through 51 which are orthologous to human CYPs involved in steroidogenesis, retinoic acid metabolism and drug pollutant metabolism. Additionally, there are 47 CYP2 genes compared to 16 in humans with only two CYP2R1 and CYP2U1 recognized as orthologous based on sequence. This study provides a foundation for the use of zebrafish as a model in toxicological, pharmacological and chemical disease research. This article was authored by Perente Thiago, Sanet Juliano, Kubota Akira and others.