Hydrogenous and deuterated isomers of poly(ethylene oxide) have been capped at one end by a C6F13 fluorocarbon group. For the three molecular weights investigated (ca. 2000, 5000, and 10 000 g mol(-1)), the surface tensions of the aqueous solutions decrease over the concentration range 10(-1) to 10(-2) g mL(-1), the lowest surface tension observed being ca. 20 mN m(-1). Neutron reflectometry has been used to determine the nature, thickness, and composition of the surface excess region. At high concentrations of polymer in solution, the surface excess region has a two-layer organization, the lower layer consisting of micelles at the underside of an upper layer at the air-water interface. For the lowest molecular weight polymer, the upper layer attains a thickness that is more than twice the radius of gyration of the polymer, indicative of a highly extended configuration and adsorption to the interface by the fluorocarbon end group. The upper layer dimensions for the two higher molecular weight polymers are of the same order as their radii of gyration, and it appears that adsorption is due to both the fluorocarbon end and ethylene oxide segments in the molecule. Although the surface excess concentration for these two polymers is considerably less than that of the 2000 g mol(-1) polymer, all have surface excess concentrations that are at least 2 orders of magnitude greater than for unmodified poly(ethylene oxide). Small-angle neutron scattering has been used to define the nature of the micelles, but the low concentrations and consequent weak signals meant that insufficient detail was in the scattering to allow a quantitative description. However, the micelles of the higher molecular weight polymers appear to have a more diffuse organization than those formed by the lowest molecular weight polymer.