The present invention relates to fused 1,2,5-oxadiazole-2-oxides of the general formula I ##STR1## in which A denotes ##STR2## and X, Y, Z as well as R.sup.1, R.sup.2, R.sup.3 and n are defined as indicated in Claim 1, to processes for their preparation and to their use for the control and prevention of disorders of the cardiovascular system, in particular for the control and prevention of angina pectoris, and for the treatment of erectile dysfunctions.