The present invention is concerned with vasoconstricive [(benzodioxan, benzofuran or benzopyran)alkylamino]alkyl substituted guanidines having the formula ##STR1## the pharmaceutically acceptable acid addition salts thereof, and the stereochemically isomeric forms thereof, wherein X is O, CH.sub.2 or a direct bond; R.sup.1 is hydrogen or C.sub.1-6 alkyl; R.sup.2 is hydrogen, C.sub.1-6 alkyl, C.sub.3-6 alkenyl or C.sub.3-6 alkynyl; R.sup.3 is hydrogen or C.sub.1-6 alkyl; or R.sup.2 and R.sup.3 may be taken together to form a bivalent radical of formula --(CH.sub.2).sub.m --, wherein m is 4 or 5; or R.sup.1 and R.sup.2 taken together may form a bivalent radical of formula --CH.dbd.CH-- or of formula --(CH.sub.2).sub.n --, wherein n is 2, 3 or 4; or R.sup.3 may represent a bond when R.sup.1 and R.sup.2 taken together form a bivalent radical of formula --CH.dbd.CH--CH.dbd., --CH.dbd.CH--N.dbd., or --CH.dbd.N--CH.dbd.; R.sup.4 is hydrogen or C.sub.1-6 alkyl; Alk.sup.1 is a bivalent C.sub.1-3 alkanediyl radical; A is a bivalent radical of formula: ##STR2## wherein each R.sup.5 is hydrogen or C.sub.1-4 alkyl; wherein each R.sup.6 is hydrogen or C.sub.1-4 alkyl; Alk.sup.2 is C.sub.2-15 alkanediyl or C.sub.5-7 cycloalkanediyl; and each p is 0, 1 or 2; provided that [2-[(2,3-dihydro-1,4-benzodioxin-2-yl)methyl]amino]ethyl guanidine is excluded. Pharmaceuticals which are useful as vasoconstrictors. Compositions comprising said guanidine derivatives as active ingredients, processes for preparing said guanidine derivatives and novel N-cyano guanidine, intermediates; and a use as a medicine are described.