Silver bream (Blicca bjoerkna Linnaeus, 1758), Roach (Rutilus rutilus L. 1758), Rudd (Scardinius erythrophthalmus L. 1758), Common carp (Cyprinus carpio L. 1758), Tench (Tinca tinca L. 1758), Northern Pike (Esox lucius L. 1758), Fresh water mussels (Anodonta cygnea L. 1758, Dreissena polymorpha Pallas, 1771), crayfish (Astacus leptodactylus Eschscholtz, 1823), and surface sediment samples were collected through the period July 2001-May 2003 from the Sapanca Lake, Turkey, and analyzed to measure the levels of heavy metals (Zn, Pb, Cu and Cd) by using Atomic Absorption Spectrometry (AAS). Cu and Zn were analyzed by air-acetylene flame, Pb and Cd by the graphite furnace technique using an argon-air mixture, and Hg by a Hg analyzer. Important differences in heavy metal contents between surface sediment and fish samples were detected. The highest metal levels were calculated in the surface sediment samples. Levels of heavy metals in muscle tissues of fish samples were calculated to be lower than liver tissue, sediment and freshwater mussel samples. The concentrations were below the limits proposed by the FAO/WHO for fish. Heavy metal concentrations in sediment were found to be higher than the allowed legal levels. It was observed that there were no statistically significant differences among the results of analyses, with respect to dates of sampling.