Phase behavior of poly(styrene-b-isoprene-b-styrene) (SIS)/tackifier resin blends were investigated by thermal analysis, morphological observation and cloud point measurements. In the heating process, the blends showed lower critical solution temperature phase transition at around 150 degrees C and upper critical solution temperature (UCST) phase transition at around 200 degrees C. However, in the cooling process, only UCST phase transition was observed in the SIS/tackifier resin blends. Tn addition, it was found that properties of the pressure sensitive adhesive in SIS/tackifier resin blends were changed with annealing temperature corresponding to the phase behavior. (C) 2000 Elsevier Science Ltd. All rights reserved.