Yessotoxins are lipophilic, sulfonated polyethers that belong to the group of marine phycotoxins, produced by algae, most often dinoflagellates of the species Protoceratium reticulatum, Lingulodinium polyedra and Gonyaulax spinifera. From the first discovery, when they were isolated from the species Patinopecten yessoensis in Japan, until today, their presence is increasing all over the world, and over time numerous analogues have been discovered. Various researches and analyzes were carried out, which clarified to some extent the mechanisms of action and toxicity of these toxins. The cytotoxic activity of yesotoxin was determined through changes in the cellular level of calcium and cAMP, caspase activation, opening of mitochondrial transition pores and modifications of the cytoskeleton. In addition, it also affects the immune system, glucose metabolism and has an interesting effect in the treatment of Alzheimer's disease. Since no cases of human poisoning have been reported, the European Union increased the limit of yesotoxin in shellfish from 1 to 3.75 mgYTX/kg of shellfish for prevention.