The Galveston Bay system was studied from Morgan 's Point, where the Houston Ship Channel joins the Bay, to Bolivar Peninsula and Galveston Island. This area includes Trinity, East and West Bays. Sample collection sites were selected near suspected point and nonpoint sources of pollution. Site 1 represents a point source from the Galveston sewage outfall. Sites 2 and 3 are point sources from the Houston Ship Channel and Texas City Channel. Site 4 is a nonpoint source. Sites 6, 7, and 8 are point sources polluted from oil platforms. Site 5 was believed to be relatively unpolluted. Total DDTs ranged from less than 0.1 to 3.5 ng per liter, with an average concentration of 0.38 ng/liter. PCB concentrations ranged from less than 0.01 to 70 ng/liter, with an average of 3.1 ng/liter. DEHP concentrations ranged from less than 2 to 12,000 ng/liter, with an overall average of 600 ng/liter. Total DDT values reported for sediments from the Mississippi Delta and along the Gulf Coast were substantially higher than those in the Galveston Bay area. PCB concentrations along the Mississippi Delta ranged from 0.2 to 35 ng/g, while along the Gulf Coast concentrations in sediments were 0.2 to 6 ng/gram with an average of 2.0 ng/gram. DEHP concentrations along the Mississippi Delta sediments ranged from less than 0.1 to 250 ng/g, with an average of 69 ng/g. Concentrations for sediments along the Gulf Coast ranged from 3.4 to 14 ng/g with an average of 6.6 ng/g. This study revealed that the relative concentrations were greatest for DEHP and lowest for DDTs in both water and sediments. (Baker-FRC)