The interaction between sodium dodecyl sulfate (SDS) and ethyl(hydroxyethyl)cellulose (EHEC) has been investigated at different temperatures by means of surfactant and counterion self-diffusion, conductivity, and time-resolved fluorescence quenching. A strengthened polymer-surfactant interaction with increasing temperature is demonstrated in several ways : in particular, a reduced critical micelle concentration, a reduced cooperativity in surfactant binding to the polymer, a decreased degree of counterion binding, and a lowered micelle aggregation number as temperature is increased. In the absence of polymer, these quantities are apparently higher and approximately invariant on temperature changes. The information on the polymer-surfactant interaction provides insight into the thermal gelation in aqueous mixtures of a nonionic polymer and an ionic surfactant.