Sediment samples were collected by the U.S. Army Corps of Engineers from the Houston Ship Channel before maintenance dredging in 1976, 1983, and 1986. These samples were analyzed for heavy metal, organochlorine pesticides, oil and grease, and some polycyclic aromatic hydrocarbons (PAH). Residue data indicate some contaminants were at levels that may produce adverse impacts on Galveston Bay biota if the contaminants migrate from the sediment during dredging or other disturbances of the material. Arsenic, copper, and zinc were hundreds of times higher in the sediment than their corresponding water quality criteria established by the U.S. Environmental Protection Agency (EPA) to protect saltwater aquatic life. Kinetics of these metals in reduced sediment during disturbances allows toxic forms of each metal to be mobilized into the Galveston Bay water columns at levels that exceed chronic toxicity values for estuarine species. These metals continuously dissolve and precipitate in unending cycles as water temperature, salinity, alkalinity, pH, and dissolved oxygen change.