The concentrations of 12 polycyclic aromatic hydrocarbons (PAHs) were determined from 28 sediment samples taken from the Lake Iznik located in the northwest area in Turkey. Total concentration of the PAHs was observed as in the range of 17-835 ng g(-1) dry weight, with the highest values recorded offshore the cities of Iznik and Orhangazi, and the Soloz creek. According to the molecular indices, contamination of the PAHs in the lake was a mixture of the atmospheric input of high temperature pyrolytic processes and the petrogenic sources transported by the creeks. Further, the higher proportion of high molecular-weight PAHs (>85%) suggests the domination of combustion-related sources. Compared to the consensus-based sediment quality guidelines for PAHs, there are no harmful biological effects on the short term to aquatic life.