This web page discusses Ciguatera, the most commonly reported marine toxin disease in the world. The dinoflagellate Gambierdiscus toxicus produces ciguatoxin throughout tropical regions of the world; it is transmitted to humans by consumption of contaminated reef fish such as barracuda, grouper, and snapper. This page describes clinical presentation (symptoms), diagnosis, management and treatment, chemical structure of ciguatoxin, and molecular mechanism of action.