Abstract: 2,4-Diaminoquinazolines of the formula ##STR1## wherein Y.sup.1 is hydrogen or chloro, Y.sup.2 is OR, Y.sup.3 is hydrogen or OR such that when Y.sup.1 is hydrogen, Y.sup.3 is OR and when Y.sup.1 is chloro, Y.sup.3 is hydrogen or OR, and the pharmaceutically acceptable salts thereof; R represents an alkyl group having from one to three carbon atoms;taken separately, R.sup.1 and R.sup.2 are each hydrogen, alkyl having from one to five carbon atoms, cycloalkyl having from three to eight carbon atoms, alkenyl or alkynyl each having from three to five carbon atoms or hydroxy substituted alkyl having from two to five carbon atoms, when taken together with the nitrogen atom to which they are attached R.sup.1 and R.sup.2 form a substituted or unsubstituted heterocyclic group optionally containing an atom of oxygen, sulfur or a second atom of nitrogen as a ring member; their use as antihypertensive agents, pharmaceutical compositions containing them and intermediates for their production.