melting behaviour of syndiotactic polystyrene (sPS) and its blend with poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) was examined by differential scanning calorimetry (d.s.c.), and the polymorphism of sPS was also investigated by X-ray diffraction. Both pure sPS and sPS/PPO blends showed three melting endotherms under our crystallization conditions. When the d.s.c. results are compared with the X-ray patterns, it is suggested that the lowest and middle melting endotherms are due to the melting of beta-and alpha-forms of sPS, respectively, whereas the highest melting endotherm comes from the melting of recrystallized sPS crystals formed during the d.s.c. scan. It is also observed that the recrystallization of sPS in sPS/PPO blends is disturbed by the presence of PPO.