Abstract: The novel acylated guanidines, ureas and substituted ureas correspond to the general formula: ##STR1## in which R.sub.1 repesents a substituted or unsubstituted aromatic ring, R.sub.2 represents an alkyl, aryl, or arylalkyl group, R.sub.4 repesents hydrogen or a variously substituted aryl group, X is oxygen or an imine group: NH and Y represent an alkyl aryl alkyloxy or aryloxy group or a hydrogen atom when X represents oxygen or the group COR.sub.3 with R.sub.3 representing an aromatic group, an aryloxy, aralkyloxy or alkyloxy group when X represents the NH group. They are prepared by heating an appropriate compound under reflux with an oxyaminoalcohol, in a suitable solvent. The products are useful as medicaments for the treatment of arterial hypertension, ischemica diseases of the heart and rhythmic disorders of the latter.