This paper summarizes what is known about the endocrine systems of mollusks and how they can be disrupted by exogenous substances. It then examines the various possibilities for using mollusk-based toxicity tests to detect and assess the environmental risks of endocrine-disrupting chemicals (EDCs). It is concluded that there are no internationally standardized tests with mollusks available at present that are suitable for assessing the risks of long-term exposure to EDCs but that several published methods show potential. At the present state of knowledge, the most promising mollusk species for use in partial life cycle testing is probably the fresh- and brackish-water mesogastropod, Potamopyrgus antipodarum, which is known to be responsive to both direct and indirect androgens and to estrogens (and their mimics). Less experience of full life cycle testing exists with mollusks, but the freshwater pulmonate gastropod Lymnaea stagnalis at present offers the best possibility for a practical procedure. In both cases, there is a need for substantial test optimization and validation before these procedures could form the basis of international guidelines.