Metal concentrations in surficial marine sediments collected from many parts of Chaleur Bay are significantly higher than background levels. The bay receives metals from various sources including a Pb smelter, an Hg-cell chlor-alkali plant, and numerous mined and unmined base-metal deposits. This study examines the sources, fluxes, and dispersal patterns of metals released to the bay, and the processes that control the transport and fate of these elements in the marine environment. Bottom sediments collected from 124 sites show the following ranges in metal(oid) concentrations (mg/kg): As, 2.8–74; Cd, 0.02–69; Cu, 3.4–200; Hg, <0.01–2.4; Pb, 0.3–2000; and Zn, 22–3200. Dispersion of smelter effluents and atmospheric emissions by wind and/or nearshore currents has resulted in an area of elevated As, Cd, Cu, Hg, Pb, and Zn concentrations in surficial sediments within c. 10–20 km of the smelter. The concentrations of most metals decrease sharply with increasing distance from the smelter; however, Pb concentrations exceed background levels in surface sediments throughout the bay. Lead isotope ratios suggest that the surface enrichment of Pb throughout the bay is mainly derived from smelter emissions and historical leaded gasoline combustion.