Linear free energy relationships for selected phthalate esters were used to estimate the rate constants for hydrolysis, biolysis, sediment-water partition coefficients, and biosorption required for modeling. The fate and transport behavior of dimethyl, diethyl, di-n-butyl, di-n-octyl, and di-(2-ethylhexyl) phthalate esters were assessed by use of an evaluation model, the Exposure Analysis Modeling System (EXAMS). Four EXAMS environments were defined: a pond, an oligotrophic lake, a eutrophic lake, and a river using environmental parameters representative of the Southeastern United States. Results suggest that higher molecular weight esters are not significantly transformed and that export from the ecosystem is the dominant process.