Caprolactam was copolymerized with hexamethylenediammonium adipate(6.6) and p-xylyenediammonium adipate (PXD. 6) salt to form two series of copolyamides. Pyrolysis-gas chromatography and nuclear magnetic resonance spectroscopy were used to determine copolymer compositions. Copolyamide 6/6.6 reveals reduced depression in Tm comparing with Flory''s prediction which suggests that some amount of 6.6 units are incorporated in the crystalline lattice, however it is not apparent in copolyamide 6/PXD. 6. The melting thermogram, which showed multiple peaks in either isothermmally or dynamically crystallized samples, Is thought to be due to the melting and recrystallization followed by remelting.