An epidemiological study on ciguatera fish poisoning in the French West Indies (St-Barthelemy, St-Martin and Anguilla) was conducted during the years 1985-1986. The investigation on intoxications shows a non seasonal significant prevalence. Though it was difficult to list the cases, the morbidity seems to vary between 7 and 30 per thousand. A study of fish toxicity was realised; 46 different species were tested (individually or by pools) by the mosquito bio-test. Observations of intoxications give the following results: High risk species: Caranx bartholomaei, C. lugubris, Seriola dumerili, Lutjanus apodus, L. jocu, Pristipomoides macrophtalmus, Gymnothorax funebris, G. moringa, Scomberomorus cavalla, S. regalis, Mycteroperca venenosa, M. tigris, Epinephelus morio, Sphyraena barracuda. Intermediate species: Caranx latus, C. ruber, Lachnolaimus maximus, Lutjanus analis, L. buccanella, L. griseus, Malacanthus plumieri, Scomberomorus maculatus. Low risk species: Balistes vetula, Alectis ciliaris, Haemulon album, Bodianus rufus, Halichoeres radiatus, Priacanthus arenatus, Alphestes afer. Many species are involved in the toxic food chain. New ones have been identified, but it is difficult to determine the toxic level range. A cartography is presented but no place is free of risk. A research of Gambierdiscus toxicus, the causal agent, on algal surface from dead corals was conducted around St-Barthelemy and St-Martin. The dinoflagellate is found in low or medium populations all around the islands with no difference between North and South. There is a maximal activity during the spring. A model of the epidemiology of the ciguatera in the area is proposed.