Abstract: The Gulf of Erdek is located in southwest Marmara Sea. Average and maximum depths are around 34 and55 m, respectively. The study area is less polluted by pollutants of anthropogenic origin than the other gulfs (Izmit,Gemlik) in the Marmara Sea. The main source of fresh water and sediments in the gulf are the Gönen and KarabigaRivers. These rivers, which receive pollution load from domestic, industries (ceramic factories and leather industry)and agricultural waste water from Gönen and Biga towns, drain in the Marmara Sea. In this study, distribution ofhistorical heavy metal contamination derived from anthropogenic and/or natural origin was investigated in a 174-cm long core sediment collected from the mouth of the Gönen River at -16 m water depth. Heavy metal enrichmentin the region was determined by analysing heavy metal (Cu, Pb, As, Zn, Cr and Co), grain size and total organiccarbon (TOC) contents. According to the results obtained, average Cu, Pb, Zn, Cr and Co values in the core are 16,68, 10, 26, 111 and 4 mg.kg-1, respectively. The mean distribution of gravel, sand, silt and clay are 0.1, 1, 28.5 and70.4%, respectively. TOC values range between 0.5 and 1.9%. Enrichment factor (EF) was calculated throughout the core to reveal the pollution history of the study area more clearly. Mean EF values through the vertical profile ofthe core are EF-Pb 12.2, EF-As 4.8, EF-Cr 3.3, EF-Zn 1.1, EF-Cu 0.9, and EF-Co 0.7. Based on Sutherland’s (2000)enrichment factor contamination categories, core sediments were moderately contaminated with Cr and As, andcontaminated significantly with Pb. The study area was not contaminated with Co, Cu and Zn. The EF-Pb, EF-Asand EF-Cr values indicate that untreated anthropogenic waste water with agricultural and industrial origin (leatherindustry) was supplied in  the gulf.