This book presents a state of the art of knowledge relating to the endocrine system of crustaceans and more particularly, amphipods and this with a particular interest in the molting gland and ecdysteroids, endocrine system disruptors, amphipods, mainly, those that affect the physiological processes controlled by ecdysteroids (molting, reproduction and embryogenesis. The knowledge provided is very important for the development of in vitro toxicity tests.