Ten of such polyacylthioureas have been synthesized through the reactions of adipic，azelaic and terephthalic diisothiocyanates with hydrazine，ethylenediamine，hexamethylerie-diamine，p-phenylenediamine and benzidine respectively．ne structure of the polymers obtained have been confirmed by elementary analysis，degradation examination，ultra-violet as well as infra-red spectroscopy．These polymers were coloured(yellow to orange) powder，sparingly soluble in common organic solvents but readily soluble in dimethylformamide and cold conc．sulfuric acid．The x-ray diffraction patterns showed that these polymers possessed fair crystallinity．The softening points of the polymers decreased with increasing length of the aliphatic carbon—chain and increased when ben- zene nuclei were introduced into the chain． Four out of these polymers possessed sof-tening points higher than 300℃．