The present invention relates to acylguanidino derivatives of formula (I), in which R.sup.1, R.sup.2, R.sup.3, A, B, X, Y and n have the meanings indicated in claim 1, their physiologically tolerable salts and their prodrugs. The compounds of the formula (I) are valuable pharmaceutically active compounds. They are vitronectin receptor antagonists and inhibitors of cell adhesion and bone resorption by osteoclasts. This renders them suitable, for example, for the therapy and prophylaxis of illness which are based on the interaction between vitronectin receptors and their ligands in cell-cell or cell-matrix interaction processes or which can be prevented, alleviated or cured by influencing such interactions. For example, they can be applied for treating and preventing osteoporosis, or for inhibiting undesired angiogenesis or proliferation of cells of the vascular smooth muscles. The invention furthermore relates to processes for the preparation of compounds of the formula (I), their use, in particular as pharmaceutical active ingredients, and pharmaceutical compositions comprising them ##STR00001##