Dinoflagellates are phytoplanktonic organisms. They are adapted to a variety of habitats: from pelagic to benthic, from temperate to tropical seas, and from estuaries to freshwater. Many dinoflagellate species can produce various toxins. Some dinoflagellate species form massive toxic or non-toxic harmful algal blooms (commonly known as “red tides”). Dinoflagellates are important marine primary producers, but also the major causative agents of harmful algal blooms. These toxins can be extremely toxic and many of them are effective at far lower dosages, toxins can be quickly carried up the food chain and indirectly passed onto humans. The poisoning can result in gastrointestinal illness, permanent neurological damage, or even death. Harmful algal blooms, except for the effects on the marine ecosystem (causing mass mortality of fish, birds, marine mammals) they produce also socioeconomic problems that adversely affecting the fishing and mariculture. Dinoflagellates cause: paralytic shellfish poisoning, neurotoxic shellfish poisoning, diarrhetic shellfish poisoning, ciguatera fish poisoning, and toxins that cause them are saxitoxin, brevetoxin, ciguatoxin, maitotoxin, okadaic acid, pectenotoxins, dinophsistoxins, yessotoxin. Because of their bioactivity, influence on safety of seafood, and potential medical and other applications Dinoflagellate toxins are of increasing interest in researches.