There has been a rapidly growing interest in the impacts of potential endocrine disrupters on humans and the environment since the early 1990s. To date, most studies have focused on evaluating effects of potential endocrine disrupters on vertebrates, whereas significant less attention has been paid (and this continues to be the case) to effects on invertebrates. Invertebrates constitute the majority of animal biodiversity on this planet, their abundance greatly exceeds that of the vertebrates, and many invertebrates have key ecological functions and important economic value. Ecdysteroids are key hormones in insects, crustaceans, and other arthropods, and there is increasing laboratory and field evidence that ecdysteroid signaling can be disrupted by chemicals in the environment. In this chapter, we give an overview of the current scientific knowledge that emphasizes the importance of ecdysteroids in invertebrate endocrine disruption research and we present future research needs.