Pollution of polycyclic aromatic hydrocarbons (PAHs) in the aquatic environment has drawn much attention around the world. The occurrence of 16 priority PAHs in the sediments and corresponding porewaters in Lanzhou Reach of Yellow River, China. and their partitioning behavior between the two phases were investigated. The results demonstrated that the total PAH levels in the sediments were positively correlated with the sediment clay contents (R-2 = 0.756). Concentrations of total PAHs in porewaters ranged from 48.2 to 206 mu g/L, and indeno[1,2.3-cd]pyrene (InP) was the most abundant compound measured in the porewater samples with a mean value of 42.9 mu g/L. The compositions of PAHs in porewaters were dominated by their compositions in the sediment samples. The in situ organic carbon normalized partition coefficients (log K-oc') of the PAHs between sediments and porewaters were significantly correlated with their octanol-water partition coefficients (log K-ow) when log K-ow values were less than 5.5 (naphthalene (Nap) excluded). log K-oc' values of 14 PAHs were lower than those predicted by the Karickhoff relationship. This discrepancy was largest for InP, dibenzo[a,h]anthracene (DBA), and benzo[ghi]perylene (BgP). The results in present study showed the tendency of PAHs release from sediment to porewater, indicating that PAHs sequestered in the sediments may be a pollution source to aquatic ecosystem. (C) 2008 Elsevier B.V. All rights reserved.