Abstract: The invention relates to a process for the manufacture of noncellular polyurethane elastomers by reacting 4,4'-diisocyanato-1,2-diphenylethane or diisocyanato-1,2-diphenylethane isomer mixtures with a 4,4'-diisocyanato-1,2-diphenylethane content in excess of 95 percent by weight, higher molecular weight polyhydroxyl compounds and low molecular weight chain extenders optionally in the presence of auxiliaries and additives.The polyurethane elastomers produced in accordance with this invention excel by a greater hardness and improved mechanical properties compared with polyurethane elastomers based on 4,4'-diphenylmethane diisocyanate with otherwise comparable composition.