Polysulphide amide (PSA) is synthesized by the displacement polymerization between 4,4＇-bis(p chlorophenyl carbonyl amino) diphenyl ether and anhydrous sodium sulphide in NMP at 200 degrees C. PSA is soluble in aprotic solvents and is characterized by elemental analysis, IR and H-1-NMR spectroscopy, and viscometry. Thermal behaviour of PSA is studied by TGA, DSC and TMA. The polymer shows good thermal stability and LOI value of about 44. X-ray analysis reveals that PSA is crystalline and has similar orthorhombic unit cell parameters to those of PPS and PEEK. The chain symmetry pattern of these three polymers is also very similar. The higher thermal stability of PSA appears to be due to higher degree of crystallinity and hydrogen bonding.