Athens basin drains by gravity to the coast into the Phaleron Bay by the Kifissos river. The Phaleron coast is currently undergoing extensive remodelling and is scheduled for development as a major amenity and recreational centre. Thus, an assessment of the Phaleron Bay's present water quality constitutes a prerequisite for the future environmental management of its waters. Analysis of oceanographic data, collected during 1989–1990, showed that eutrophic conditions prevail in the vicinity of Kifissos river, where nutrients and chlorophyll-a occur in high concentrations. Also in this area, the benthic communities have been modified and they are dominated by detritus or sediment feeding polychaetes. However, beyond this region the impact of the river discharge diminishes with distance offshore and in the entrance of the bay, both water column quality and benthos are indistinguishable from those of the open Saronikos Gulf.