The thermally induced phase separation of aqueous poly (N,N-diethylacrylamide) (PDEA) was studied by means of differential scanning calorimetry and US＇-visible spectrophotometry. The polymer was shown to have a well-defined lower critical solution temperature (LCST) of 33 degrees C. The addition of sodium chloride to the polymer solution resulted in a linear decrease of the LCST, Sodium dodecyl sulfate, at concentrations up to its critical micelle concentration, caused a gradual increase in the LCST of PDEA.