An integrated ecological investigation of Saronicos Gulf, Aegean sea, was made with the objective of studying the phytoplanktonic populations of the area in connection with the detection and quantitation of species indicators of sewage pollution.The data used comprise the results of thirty six surveys made during January - December 1980.Quantitative and qualitative data of phytoplankton populations collected monthly from nine stations are reported.The stations consisted of three transects of three stations each, from inshore to offshore waters.