The present study examines the concentrations of Cd, Cu, Mn, Ni, Pb and Zn in 2004 in the Saronikos Gulf, an embayment affected by anthropogenic inputs from the nearby metropolitan area of Athens. We investigated in particular the impact of the operation for a decade of the primary Wastewater Treatment Plant of Athens, which is located at Psittalia Island, on the levels of these metals in the marine environment of the gulf, few months before the inauguration of the secondary treatment. Therefore, the present work represents the needed baseline for any future comparisons and assessment of the impact of the secondary treatment. For two samplings carried out in May and September 2004 in a grid of fifteen stations, dissolved and particulate metal concentrations are, respectively, in the range 5.0-63 and 0.22-3.6 ng/L for Cd, 0.03-0.72 and 0.03-0.23 mu g/L for Cu, 0.11-1.2 and 0.02-0.55 mu g/L for Mn, 0.19-1.5 and 0.01-0.11 mu g/L for Ni, 0.05-0.60 and 0.02-0.59 mu g/L for Pb and 0.13-5.8 and 0.06-1.0 mu g/L for Zn. The concentrations of the majority of the studied metals obtained in 2004 are comparable to those of the year 2000 and among the lowest detected in the Saronikos Gulf ever since the beginning of the MED-POL program twenty years ago. This stabilization is attributed to the operation of the wastewater treatment plant and offers an indication that the levels of trace metal pollution of the marine environment of the gulf are possibly reaching a steady state.