The mono and polyester glycosyl sulfates or phosphate diglycerides account for a group of polar lipids which is found in large amounts in the three fucacae that are studied: Pelvetia canaliculata (L) Deen and Thur, Fucus vesiculosus (L), Fucus serratus (L). These polar lipids have been shown to have complex structures, most of them are unknown in the present nomenclature. Both quantity and composition of these polar lipids are species characteristics, forming the equipment of polar lipids for every species of algae. Glycosyl ester sulfate and phosphate diglycerides are very unstable substances when pure, moreover photolabile and thremodegradable. This extreme fragility caused many difficulties in the determination of molecular structures which require a very high purity of isolated substances, The determination of the structures, studies of quantities and composition cytological localization of these polar lipids should allow to define clearly their physiological function and importance from the biochemical and ecological point of view.