We report the use of surface quasi-elastic light scattering (SQELS) to investigate the dynamic surface properties of spread films of cyclic poly(ethylene oxide) at various surface concentrations of polymer. Application of an unbiased phenomenological fitting function to the collected heterodyne correlation functions allows the frequency and damping of the capillary waves to be measured. Increasing the surface concentration of polymer causes complex variations in the capillary wave frequency and damping which can only be explained by the existence of a resonance between the capillary and dilational waves. We further analyze the correlation functions in terms of four surface viscoelastic parameters-surface tension, transverse shear viscosity, dilational modulus, and dilational viscosity-via a direct "spectral fit" to the data. At surface concentrations where the surface is saturated with polymer, at least one relaxation process occurs in the frequency regime studied. For the dilational mode of the interface, this relaxation is associated with the rate of desorption of polymer chains from the interface into the subphase when the surface is saturated with polymer. Both viscosities have unusual properties-the transverse shear viscosity decreases at intermediate surface concentrations before increasing again with surface concentration, and the dilational viscosity is always negative. This apparently unphysical measurement may have two origins : either a coupling with another surface oscillation mode or, because the dispersion equation does not describe the surface behavior completely, an idea supported by the discrepancy between the capillary wave dampings calculated from the observed surface viscoelastic parameters and those measured directly.