The toxicity of sediments in the Maumee River, the Maumee River-western Lake Erie federal navigation channel, and selected areas of western Lake Erie was measured using four assays: Photobacterium phosphoreum 15-minute bioluminescence inhibition (Microtox) in sediment porewaters and elutriates; Ceriodaphnia dubia 7-day survival and reproduction; Pimephales promelas 7-day larval survival and growth in sediment elutriates; and Chironomus tentans 10-day growth inhibition in whole sediments. The Microtox assay generally was the most sensitive of the four assays used in the investigation. Sediment elutriates were always equally or more toxic than porewaters from the same location when tested using the Microtox assay. The greatest toxicity in the Microtox and C. tentans assays was observed with porewaters or elutriates and sediments collected near point sources of contaminants to the Maumee River. Very little toxicity was observed in any assay using open-lake navigation channel or disposal site sediments or sediment extracts. Previous investigations also have reported little acute toxicity and little or no bioaccumulation of any measured sediment contaminants from study area sediments during laboratory toxicity or bioaccumulation assays. Sediments from the Lake Erie portion of the navigation channel evaluated during the investigation were suitable for open-lake disposal based on the lack of observed effects in the four assays.