Marine sediments and bivalves were sampled at 20 stations from coastal regions of Korea, to investigate the levels and patterns of some chlorobenzene isomers. Total chlorobenzenes were in the range of 0.32-3.55 ng/g dry weight in marine sediments and 0.26-0.84 ng/g wet weight in bivalves. Hexachlorobenzene levels in marine sediments and bivalves were lower thar or comparable to those levels of reported in other countries. Isomeric patterns of some chlorobenzenes in marine sediments and bivalves were slightly different. However, the pre-dominant isomer in marine sediments and bivalves was 1,2,4-trichlorobenzene. Hexachlorobenzene contribution to total concentrations was higher in sediments than in bivalves.