Perfluorinated surfactants are an important class of specialty chemicals that have received recent attention as a result of their persistence in the environment. Two analytical methods for the determination of perfluorinated surfactants in aqueous samples were developed in order to investigate a spill of 22000 L of fire retardant foam containing perfluorinated surfactants into Etobicoke Creek (Toronto, Ontario). With the first method, aliquots of surface water (0.2-200 mL) were preconcentrated using solid-phase extraction. Liquid chromatography/tandem mass spectrometry was employed for identification and quantification of each perfluorinated surfactant. Total perfluorinated surfactant concentrations in surface water samples ranged from 0.011 to 2270 microg/L, and perfluorooctanesulfonate was the predominant surfactant observed. Interestingly, perfluorooctanoate was detected in surface water sampled upstream of the spill. A second method employing 19F NMR was developed for the determination of total perfluorinated surfactant concentrations in aqueous samples (2-100 mL). By 19F NMR, the surface water concentrations ranged from nondetect (method detection limit, 10 microg/L for a 100-mL sample) to 17000 microg/L. These methods permit comprehensive evaluation of aqueous samples for the presence of perfluorinated surfactants and have applicability to other sample matrixes.