ΣDDT residues in the St. Lucie River bottom sediments increased after Lake Okeechobee water was discharged through the St. Lucie Canal into the area. ΣDDT levels were highest in sediment samples from the Palm City area, ranging from 1.8 ppb to 6.15 ppb. Sediment samples from the A1A Highway Bridge area contained 1.6-6.8 ppb Aroclor 1254. Levels of polychlorinated biphenyls (PCBs) and ΣDDT in sediment samples from the junction of the St. Lucie and Indian Rivers were not detectable. Surface water samples from the estuary did not show any detectable DDT or PCB residues.