High molecular-weight organic polyelectrolytes (polymers) have been used successfully to flocculate raw wastewater and to increase the removal of pollutants from the wastewater during primary sedimentation. At present, however, a satisfactory method for predicting the effectiveness of a particular polymer for flocculating solids in a specific wastewater is not available. Three polymers, Dow's anionic A-21 modified with cationic C-31, Hercules' cationic Reten 210, and Calgon's anionic ST 269 with a clay builder, were added to raw wastewater in 240 MGD tests of raw wastewater flocculation. The objectives of polymer flocculation of the raw wastewater were to increase solid capture in the primary tanks, reduce the BOD load to aeration, and permit recycle of the elutriate to the plant's influent. Polymer treatment of raw wastewater did not improve the solids capture in elutriation or permit continuous elutriate recycle.