The lower Willamette River, located between river mile 4.0 and 26.5, is the most seriously polluted section of the Willamette River Basin. Low dissolved oxygen concentrations of 2.0 to 3.0 mg/1 are observed annually in this section of the river due to the pollutional loads discharged into it. Waste discharges originate from upstream sources, from two large pulp and paper mills at river mile 26.5, treated domestic sewage from several small communities, from several sewer outfalls in the Portland Harbor, and from other miscellaneous sources. These total waste loads discharged, during the summer low flow period, are equal in pollutional capacity to the wastes from an equivalent population of 484,000. Of this total load, wastes from the two pulp and paper mills account for an equivalent population of 350,000. A better understanding of the dissolved oxygen resources of this section of the river is necessary for water quality management. Analyses of the dissolved oxygen resources in this section of the river indicate that sludge deposits may be located in the river between river miles 26.5 and 19.0. These deposits exert a large demand on the dissolved oxygen present. The magnitude of this dissolved oxygen demand is about 34,000 pounds per day. Results of this study indicate that the source of this pollutional loading originates between river miles 26.5 and 19.0. It is further indicated that a detailed on-site survey of this section of the stream and possible waste contributors should be undertaken to provide information necessary for restoration of water quality.