During the past 20 years, the role of sediment toxicity tests has expanded from testing of primarily dredged material to risk assessment, decontamination technologies, large-scale regional sediment-quality assessments, and toxicity identification evaluations. Sediment toxicity tests are needed that can provide reliable data using less sediment and smaller test chambers, thus utilizing resources more efficiently. We compared survival results from 10-d standard marine amphipod tests at 20 degrees C using 200 ml of sediment to reduced-volume tests containing 20 or 50 ml of sediment and found no significant differences. Similar survival also was observed in tests conducted for 7-d at 23 degrees C versus the standard 10-d exposure at 20 degrees C. However, amphipod sensitivity was significantly less in reduced-volume tests conducted for only 4- or 7-d at 20 degrees C. The 10-d sediment toxicity tests using 50 ml of sediment provided comparable results to the standard protocol, whereas time for sampling, preparing, and sieving sediments for a test was substantially reduced.