Cytolytic peptides have commanded attention for their anticancer potential because the membrane-disrupting function that produces cell death is less likely to be overcome by resistant mutations. Congruently, peptides that are involved in molecular recognition and biological activities become attractive therapeutic candidates because of their high specificity, better affinity, reduced immunogenicity, and reduced off target toxicity. However, problems of inadequate delivery, rapid deactivation in vivo, and poor bioavailability have limited clinical application. Therefore, peptide drug development for clinical use requires an appropriate combination of an effective therapeutic peptide and a robust delivery methodology. In this chapter, we describe methods for the postformulation insertion of peptide drugs into lipidic nanostructures, the physical characterization of peptide-nanostructure complexes, and the evaluation of their therapeutic effectiveness both in vitro and in vivo.