The distribution of polychlorinated biphenyl (PCB) compounds in Puget Sound is discussed in terms of the physical and chemical processes that influence their flow throughout the estuary. These data were used to examine the accumulation of PCBs in suspended phases and in lower trophic level biota. At the low PCB levels detected in this region, the data suggest that accumulation is predominantly governed by an equilibrium-partitioning mechanism. Support for the applicability of partitioning constants is presented, together with a discussion of their utility in describing the general distribution of PCBs in the aquatic environment.