Polyamides containing 1,4-dithiin-2.3:5.6-tetrayl diimide structures were synthesised by condensation reaction of bis[N,N'-(4-chlorocarbonylphenyl))- 1.4-dithiin-2.3:5.6-tetrayl diimide] (3) with various aromatic diamines. Monomer 3 was synthesised by nucleophilic substitution of N-(4-carboxyphenyl)-3.4-dichloromaleimide (1) with sodium sulfide nonahydrate. Their structures were confirmed by IR and UV spectroscopy, as well as elemental analysis. The polymers were characterised by viscometric measurements, softening points and thermogravimetric data. They showed good solubility in aprotic solvents and high thermal stability with the decomposition temperature being in the range 392-415 C.