The miscibility of syndiotactic polystyrene (sPS)/atactic polystyrene (aPS) blends, whose constituent polymers have close T(g)s was investigated by crystallization kinetics and enthalpy relaxation. It was observed from crystallization kinetics experiment that both the spherulite growth rate and the overall crystallization rate of sPS in blends decrease with an increasing amount of aPS, indicating that sPS is diluted with aPS. When enthalpy relaxations of the blends are examined, it is revealed that the enthalpy recovery of sPS/aPS blends shows a single peak whose relaxation time is intermediate between those of sPS and aPS, and that the relaxation time of the blends gradually increases with the amount of aPS. From these results, it is concluded that sPS/aPS blends are completely miscible over the entire composition.