Some species of the dinoflagellate genera Dinophysis and Prorocentrum can produce powerful toxins that affect human health by consumtion of poisoned shellfish (Diarrhetic Shellfish Poisoning, DSP), whereas Gambierdiscus toxicus has been associated with Ciguatera fishfood poisoning, in tropical areas. In the Mexican Caribbean, there is no taxonomic study of phytoplankton and benthic microalgae. Material recently collected from various points along the coasts of the Mexican Caribbean: plankton by net (54 mm), sediment and epiphytes from large macroalgae and other plants, was used to study the toxic, potentially toxic and associated dinoflagellates. We recorded the presence of known toxic species: Dinophysis hastata, D. rotundata, Gambierdiscus toxicus, G. yasumotoi, Prorocentrum lima, and P. mexicanum, plus other associated species: Gambierdiscus belizeanus, Prorocentrum hoffmanianum and Pyrodinium bahamense var. bahamense. Some of these species are truly planktonic forms: Dinophysis spp. and P. bahamense var. bahamense, whereas other are benthic and epiphyte forms: G. belizeanus, G. toxicus, G. yasumotoi, P. lima, P. hoffmanianum and other Prorocentrum species, all distributed in shallow coastal areas and coastal lagoons. The three species described for the genus Gambierdiscus are found in the study area. Most of the species have been studied by light and scanning electron microscopy. We have not made studies to detect toxins production of the dinoflagellates recorded. No cases of Ciguatera or DSP have been properly documented in detail in this region, although unofficial reports point to several cases of Ciguatera by comsumption of fish.