Laboratory survival tests were conducted with an indigenous infaunal amphipod, Corophium colo, on 103 sediment samples from Sydney Harbor (NSW, Australia) and vicinity, containing a wide range of chemicals and concentrations. The present study describes the sensitivity of C. colo to the sediments and compares the results to data for North American amphipods (Rhepoxynius abronius and Ampelisca abdita) previously used to establish and validate sediment-quality guidelines (SQGs). The incidence of toxicity increased with increasing contamination, as indicated by increasing numbers of SQGs exceeded and increasing mean SQG quotients. The incidence of highly toxic results (p < 0.05 and mean amphipod survival of < 80% that of controls) for highly contaminated samples was approximately half (28-40%) that of a large U.S. database (74%). The incidence of highly toxic responses for samples with intermediate levels of contamination also was lower in the present study (5-13%) compared to the results in large U.S. studies (approximately 30-50%). Corophium colo reburial tests showed greater sensitivity compared to survival tests, with a maximum incidence of statistically significant responses in moderately contaminated sediments of 70%. The present study showed that adult Corophium organisms are suitable for testing lethal responses in highly contaminated sediments (i.e., with mean effects range-median quotients of >1.5). Reburial results provide additional sensitivity.