Sediment/soil organic matter (SOM) is the predominant sorbents for hydrophobic organic compounds (HOCs). The identification and comparison of sorption characterization of HOCs by different organic matter fractions are essential to predict the fate and transport of HOCs in soils and sediments. The objectives of this paper are to compare the sorption of benzo[alpha]phrene (BaP) to the humic acid (HA) and humin (HM) extracted from different sediments. The HA and HM were extracted with 0.1 M NaOH from five sediments in different areas in China, and their sorption isotherms for BaP were determined. All sorption isotherms were nonlinear and nonlinearity increased in the order HA < sediment < HM. BaP sorption capacities on the HA fractions were significantly related to their aliphaticity, but negatively correlated to aromatic carbon. However, more aromatic carbon in HM fractions can result in higher K-oc values of BaP than HA. This implied the importance of both aliphatic and aromatic groups in BaP sorption. HM contributed to 54-92% of the total sorption depending on initial concentrations, clearly indicating the dominance of HM in BaP sorption by the sediments. (C) 2008 Elsevier B.V. All rights reserved.