Up to now little has been written concerning the algal vegetation of the Dutch coast. Van Goor (1923) was the first investigator who occupied himself with the description of algal communities in our waters; in the western part of the Waddensea and in the former Zuyderzee he distinguished 8 “associations”. Some years later Sloff (1925-’26) described the zonation of the Fucaceae in the littoral belt of Bergen op Zoom and Koffiehoek (Island of Tholen). This subject was studied again by Zaneveld (1937), who tried to find a correlation between the position of the Fucaceae belts at Den Helder and the different tidal levels. Since 1950 the phytocenological study of the Dutch coast was taken in hand by the author with the following intentions: 1 °. to give as complete a description as possible of the epilithic algal communities, 2°. to devise a system for the classification of these communities and 3°. to inquire into the factors which determine differentiation of the vegetation into well-characterized units.