The distribution of marine algae in Ceylon is well known but hardly any work had been done to study the algal succession in any of the littoral zones adjoining our coast. It was decided to study the algal vegetation in the littoral zone on the eastern side of Mandativu every month for a period of one year with the view to determining algal succession and seasonal variation. The study was confined to a length of one mile along the coast upto a distance of a quarter mile towards the sea. The present paper deals with the marine algae growing in this area.