The distribution of selected trace metals in water, suspended matter and sediments of southern Lake Michigan and in surficial sediments of lower Green Bay is described. Accumulations of As, Br, Cr, Cu, Hg, Pb, and Zn in fine-grained surficial sediments of southern Lake Michigan, apparently determined by patterns of sediment desposition, correlate closely with sediment concentrations of organic carbon and iron. Organic carbon concentrations of surficial sediments are more highly correlated with concentrations of Cu, Pb and Zn in surficial sediments of lower Green Bay than are either Fe or Mn contents. Mean concentrations of trace metals in suspended matter near the sediment-water interface of southern Lake Michigan equal or exceed amounts in surficial sediments. Horizontal (geographic) and vertical distributions of concentrations of nine trace metals (Cd, Cr, Co, Cu, Fe, Pb, Mn, Ni and Zn) in waters of southern Lake Michigan were examined during the period June-October, 1971.