In order to evaluate the effect of local anthropogenic activities on Chaohu Lake, one of the most eutrophicated lakes in China, surface sediments have been collected from the whole lake with 0.05 × 0.05 degree latitude/longitude resolution and in the estuaries of three main inflowing rivers. The concentrations of the 28 polycyclic aromatic hydrocarbons (PAHs) determined were in a range 82.4–13 000 ng g⁻¹ with an average value of 1670 ng g⁻¹ dry weight for total 28 PAHs (referred to as Σ₂₈PAH). Amongst the 28 PAHs, 16 are listed as high priority PAHs by the USEPA and they were in the range of 60.8–10 200 ng g⁻¹ with an average value of 1230 ng g⁻¹ for the total of them (referred to as Σ₁₆PAH); 7 are known as carcinogenic PAHs and their levels ranged from 34.2 to 6400 ng g⁻¹ with an average of 815 ng g⁻¹ in total (referred to as Σ₇PAH). Chaohu Lake was considered significantly polluted by PAHs through the comparison with the PAH burdens in fresh-water lakes both in China and worldwide. Toxic units (TUs) evaluation showed some sampling locations possibly were over the median lethal level for benthic invertebrate. The highest PAH concentrations were found in sediments from the Nanfei River estuary, suggesting the major contributor of PAHs contamination to the lake. The PAHs with four and five rings were found to be dominant among the PAHs detected in all of the sediment samples, and perylene was the most abundant. Σ₁₆PAH had a good correlation with those PAHs from pyrogenic sources, such as anthracene and phenanthrene, but a poor correlation with perylene. The results demonstrated that the environmental behavior of PAHs from pyrogenic sources is significantly different to that of perylene from diagenetic sources. The PAHs in sediments were mainly from traffic-related emission by qualitatively assessing with the diagnostic ratios of PAH isomers, and the ratios for low molecular weight PAHs were strongly altered during their transport.