Various peptide sequences have been discovered by selecting peptide-phage display libraries in vitro against specific receptors or in vivo in tumor-bearing animals. One class of these peptides is characterized by the presence of Asn-Gly-Asp (NGR), a structural motif that can recognize the endothelium and other cells of neoangiogenic vessels. Because of this property these peptides have been used by several investigators to deliver a variety of drugs, cytokines, nanoparticles, viruses and imaging agents to tumor blood vessels. Here we review the reports on these conjugates and discuss the structural, functional and stability properties of NGR embedded into different molecular scaffolds.