AbstractInterfacial polycondensation of diamines and bischloroformates has been used to prepare a wide variety of high molecular weight polyurethanes, many of which cannot be synthesized by means of the diisocyanate‐glycol addition process. Almost every type of diamine normally used in condensation polymerization, i.e., aliphatic, alicyclic, cyclic secondary, and aromatic diamines, has been found suitable. Aliphatic, alicyclic, and aromatic bischloroformates have been prepared and utilized as coreactants. Of particular interest are the polymers melting above 200°C. which have been obtained from such intermediates as piperazine, ethylenediamine, and the bischloroformates of ethylene glycol, 2,2‐dimethyl‐1,3‐propanediol, hydroquinone, and thecisandtransisomers of 1,4‐cyclohexanediol. The purity of the reactants and the type of organic solvent, acid acceptor, and dispersing agent were found to be important variables which influenced the molecular weight of the pol