Aquatic pollution has led to the accumulation of various xenobiotics in crustaceans. A number of these environmental chemicals have been found to interfere with molting of crustaceans. Results of initial mechanistic studies with Uca pugilator suggest that the disruption of molting results from the disturbance to the Y-organ-ecdysteroid receptor (EcR) axis by xenobiotics. Such disturbance to the Y-organ-EcR axis can be caused by interference with epidermal ecdysteroid signaling and/or alterations in ecdysteroidogenesis and/or ecdysteroid disposition. Because the adverse impacts on crustacean molting cannot be readily seen in the wild, the disruption of molting represents an invisible form of endocrine disruption.