Concentrations of total polychlorinated naphthalenes (PCNs) as high as 23 micrograms/g, dry wt, were found in sediments contaminated by the disposal of wastes from chlor-alkali processes. Concentrations of total PCNs in blue crab, fish and birds were 3- to 5-orders of magnitude less than that in sediments. The profile of PCN congeners in biota was predominated by tetra- or penta-chloronaphthalenes, while hepta- and octa-chloronaphthalenes were dominant in sediments. The 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQs) estimated for PCNs in sediments and biota were greater than those reported for PCBs, PCDDs or PCDFs. These results suggest that chlor-alkali process is a source of PCNs found in the environment.