Polybrominated diphenyl ethers in Lake Ontario watershed sediments were assessed for benthic bioavailability through the use of biota-sediment accumulation factors. Sediments from lake and Rochester Harbor (lower Genesee River) areas were investigated. Congeners 47, 66, 85, 99 and 100 were detected in tissues of the oligochaete Lumbriculus variegatus. Biota-sediment accumulation factors ranged from 3.95 (congener 154) to 19.5 (congener 28) and were higher at the Lake Ontario area. The lower biota-sediment accumulation factors for the Rochester Harbor sediment may result from a higher fraction of black carbon generally expected in highly urbanized rivers. Degree of bromination may reduce bioavailability.