A series of toxicity tests were conducted on liquid and suspended solid phase fractions of sediments from the Port of Hampton Roads, Virginia. The respiration and hyporegulatory capacity of grass shrimp proved to be sensitive indices of sublethal stress associated with exposure to contaminated sediments. On the other hand, hyper-regulatory capacity was not affected by any of the experimental conditions. Experiments involving sediments from Hampton Roads Harbor and most of the mainstem of the Elizabeth River showed no indications of stress. However, sediment elutriates from the most industrialized region of the Southern Branch of the Elizabeth River produced significant sublethal effects. The present study clearly defined the region of significant sediment contamination. The findings also indicated that most materials dredged during port deepening operations should be less contaminated than those routinely taken by maintenance dredging.