Polyethylene terephthalate/polyoxyethylene terephthalate (PET/POET) water-soluble polymers are effective surface modifiers of polyester-containing textiles and exhibit surface activity in aqueous solutions. Adsorption of a PET/POET polymer on fabric was studied using ultraviolet-visible (u.v.-vis) and fluorescence spectroscopy. Aqueous PET/POET solutions exhibit two distinct fluorescent emission bands, 334 nm and 386 nm, and the latter band is assigned to an intramolecular excimer of terephthalate groups. The ratio of the fluorescence intensities of these two bands (I-386/I-334) decreases upon adsorption of the polymer onto fabrics, indicating that one of the solution structures is preferentially adsorbed. Addition of anionic surfactant such as sodium dodecylsulfate (SDS) inhibits the formation of excimers whereas nonionic surfactant does not. Effects of nonionic, anionic surfactants, as well as salt effects (Na+, Ca2+) on the formation of excimers and on the adsorption behaviour were investigated using both u.v. absorption and fluorescent emission bands, cloud point, and surface techniques. Polymer-surfactant interactions were observed predominantly at surfactant concentrations below the critical micelle concentration (cmc). The apparent cme of SDS increased with increasing polymer concentration, and SDS interactions with the polymer can be explained by models previously used to describe interaction between polyethylene oxide and SDS.