Novel pyrimidinedicarbamates of the formula ##STR1## wherein R is lower alkyl or (lower alkyloxy)-(lower alkyl) and X is a leaving group, can be manufactured by carbamoylating the corresponding free diamines. They are valuable intermediates and can be used, for example, for the manufacture of corresponding oxadiazolopyrimidines of the formula ##STR2## and pharmaceutically acceptable salts thereof. The latter have valuable long-lasting vasodilating and/or bloodpressure lowering properties and are accordingly suitable especially for the treatment of vascular-conditioned hypertensions or as vasodilators in the case of peripheral blood supply disorders.