The phase behavior and crystallization of poly(ether ketone ketone)/polyimide blends was investigated by differential scanning calorimetry and dynamic mechanical analysis, and chemical interactions in the blends were probed by Fourier-transform infrared spectroscopy. Amorphous blends were miscible over the entire range of composition, although mixing was most favorable at higher thermoplastic polyimide concentrations. Blending suppressed crystallization, especially of the minor component, but crystallization of both components, however, did occur in most of the blends. While blends quenched from the melt exhibited only a single amorphous phase, melt crystallized blends appeared to possess two amorphous phases with different compositions. Shifts in the vibration frequencies of the carbonyl and imide bonds were inconsistent with the development of strong, specific intermolecular interactions, but may be explained by a disruption of the packing of the two homopolymers by nature of the mixing. (C) 2004 Wiley Periodicals, Inc.