The aim of this work was to analyze Chamelea gallina harvested in the Sea of Southern Marmara in terms of heavy metal, biotoxin, and microbiological contents. Samples were collected seasonally from five stations which were determined to be their natural habitats in the between February 2008 and January 2009. Heavy metal contents of the samples revealed statistically significant (P<0.05) differences between seasons and stations. In two stations, Pb and Zn content of the clams were determined to exceed legal limits imposed by Turkish Fisheries Regulation and EC Shellfish Hygiene Directive (91/492/EEC). Biotoxin was not detected in any sample analyzed and the counts of Escherichia coli and fecal coliform bacteria of the samples were lower than the legal limits. Salmonella spp. was not detected in the sampling stations, whereas Vibrio parahaemolyticus was isolated in two stations. In conclusion, clams harvested in the southern Marmara Sea, excluding Gelibolu and Karabiga stations, were found suitable for human consumption.