In order to determine the hazards posed by hydrophobic organic compounds (HOCs) like PAHs and PCBs in sediment beds, we have initiated a study to explore the use of small polyethylene (PE) sheets as passive sampling devices for measuring HOC chemical activities in this complex environmental compartment. Bench scale experiments showed that the chemical activities in PE brought to equilibrium with sediment samples matched porewater chemical activities within a factor of two for six PAHs (phenanthrene, anthracene, fluoranthene, pyrene, benz(a)anthracene, and chrysene) in two sediment samples. Next tracer chemicals, impregnated within the PE, were used to calibrate a mass transfer model for PE inserted in the same sediments for short times (days). Target chemical activities were then deduced using the build up of mass of these HOCs within the PE and knowing their PE-water partitioning coefficients and the aqueous solubilities. These corrected non-equilibrium results compared well with the results of the equilibration experiment, and were within a factor of two of porewater measurements. Chemical activities deduced from analyses of the sediments and normalizations using an EqP model which considers organic carbon and black carbon differed from porewater measurements by a factor of 10. Finally, PE samplers were deployed in-situ at a coal tar-polluted site in the Boston Harbor. Results of this experiment showed the vertical profile of PAH activity increasing over a depth of 20 cm. PE samplers were found to be durable enough to withstanding insertion into several types of sediment beds, including those littered with shells, rocks, and other jagged materials, and provided enough material that several analyses of the same sample were possible. We believe PE passive samplers to be well suited to measuring HOC chemical activities in sediment beds.