Phthalate ester plasticizers have been detected in the open-ocean environment. Samples consisting of water, sediment, air, and biota from the Gulf of Mexico and of water and air from the North Atlantic were analyzed and found to contain two phthalate esters, di-(2-ethylhexyl) phthalate (DEHP) and di- n -dibutyl phthalate (DBP); the concentrations of polychlorinated biphenyls (PCB's) and DDT's ( p , p ′-DDT and p , p ′-DDE) were also determined. Like the ubiquitous PCB's and DDT's, the phthalate plasticizers were found in almost all samples analyzed; DEHP was present at higher concentrations than the PCB's or DDT's in water and sediment. The environmental impact of the concentrations found in these studies, coupled with the continued high production and wide use of these plasticizers, requires assessment.