The miscibility and melting properties of binary crystalline blends of poly(ethylene 2,6-naphthalate)/poly(trimethylene terephthalate) (PEN/PTT) have been investigated with differential scanning calorimetry (DSC). The glass transition and cold crystallization behaviors indicated that in PEN/PTT blends, there are two different amorphous phases and the PEN/PTT blends are immiscible in the amorphous state. The polymer-polymer interaction parameter, chi(12), calculated from equilibrium melting temperature depression of the PEN component was -1.791 x 10(-5) (300 C), revealing miscibility of PEN/PTT blends in the melt state.