A series of measurements have been made on the dependence of the intensity and energy spectrum of slow positrons re-emitted from polycrystalline tungsten foil held at temperatures of up to 500 degreesC. Irrespective of target history, no sharpening of the energy spectrum of re-emitted positrons was observed as the remoderator temperature was increased. Further, a steady decrease in the apparent re-emitted positron intensity was observed, attributed primarily to the increase in positronium formation, as the temperature of the foil was increased from 20 to 500 degreesC. It is concluded that maintaining a moderator or remoderator at elevated temperatures in standard positron beam systems has no beneficial consequences for the quality or intensity of the beam produced. Reasons for this are discussed. (C) 2002 Elsevier Science B.V. All rights reserved.