The extent of organochlorine pesticides (OCPs) contamination in Manyas Lake (Bird Lake) and its tributary rivers and streams which is situated near the South-eastern coasts of the Marmara Sea in Turkey was investigated. Residues of OCPs in surface water and sediment samples were analysed by gas chromatography equipped with electron capture detector. The total OCPs concentration (Sigma OCPs) in water and sediment samples ranged from 1.43 to 8.6 mu g l(-1) and from 17.05 to 39.14 ng g(-1) respectively. According to the concentrations and detection frequencies, HCHs, DDTs, heptachlor and heptachlor epoxide were the most dominant compounds among the OCPs. The results showed that Manyas Lake was still contaminated by organochlorine pesticides and their residues despite bans on the production and usage over a long time.