The potential of the water in the Mississippi River in south Louisiana to result in drinking water that exceeds the EPA standards for some heavy metals was studied, using analyses of the river water obtained regularly by the Louisiana Division of Water Pollution Control. Between 1978 and 1983, river water concentrations at individual sampling sites exceeded the drinking water standards 1 to 3 percent of the time for cadmium, chromium and copper; 7 to 9 percent of the time for arsenic and lead; and 18 percent of the time for mercury. Correlations of heavy metals versus total suspended solids (TSS) suggest that arsenic, cadmium and chromium are carried predominantly by the TSS and should be removed in the usual water treatment steps of coagulation followed by settling and/or filtration. Copper and lead appear to be carried, at least partly, in dissolved form, while additional data are needed in the case of mercury.