The present work comprises the synthesis of polyacylthioureas from dicarboxylic acids and aromatic diamines. The reagents used were: terephthalic acid, isophthalic acid, amines such as benzidine and m-phenylenediamine. The method used was the addition of amines to thiocyanates. To obtain terephthaloyl thiocyanate, terephthaloyl chloride was reacted with ammonium thiocyanate, using dry acetone as solvent. To obtain isophthaloyl thiocyanate, isophthaloyl chloride was reacted with ammonium thiocyanate, also using dry acetone. In both reactions it was necessary to prepare the acid halide. Terephthaloyl dichloride was obtained from terephthalic acid, which was reacted with ammonium thiocyanate, also using dry acetone as solvent. Subsequently, several polyacylthioureas were synthesized via the addition of different amines. The products obtained were: poly- [N-terephthaloyl-N '- (4,4'-biphenyl)...