17α-ethinylestradiol (EE2) is a synthetic estrogen commonly used as an active substance in oral contraceptives. It is frequently found in waste water effluent and raise concern due to its persistent nature. EE2 binds to estrogen receptors with similar affinity to oestradiol and acts as one of the most potent hormone mimics found in the environment. Estrogen is involved in many aspects of the development of the neuroendocrine system influencing both brain structure and behavior. We and others have reported a significant effect on non-reproductive behaviors in adult fish and in recent studies we found that developmental exposure to EE2 resulted in an anxiogenic phenotype as adults even after a long remediation period. In this study we aim to study possible mechanisms behind the behavior alterations of zebrafish developmentally exposed to EE2 by sequencing the whole brain transcriptome. Zebrafish embryos were exposed to 0, 2.14 and 7.34 ng/L EE2 from 1 day to 80 days post fertilization. After the exposure period a remediation period of 120 days followed before the fish were sampled. 3 male brains from the control group (0 ng/L) and the 2.14 ng/L group were sampled and 3 female brains from the control group (0 ng/L) and 7.34 ng/L were sampled.