The specificity of peptide activity depends on the sequence of amino acids and structure, so it is easy to understand the great degree of biodiversity that peptides can cover. Accordingly, the literature shows that peptides carry out various activities, including antiproliferative, antihypertensive, antimicrobial, antioxidant, anticholesterolemic, opioid and antidiabetic activities. However, the potential activity of peptides is strongly quenched by their low bioavailability. The aim of this work is to provide some insights on the possibility of increasing the bioavailability of peptides. Two key points have been investigated. The results demonstrate that N-terminus acetylation and C-terminus amidation can strongly protect peptides from proteolytic degradation. Furthermore, the activity of the peptides can be reduced by the formation of complexes, for example through hydrophobic interactions. In particular peptides containing cysteine can dimerize with the formation of a disulfide bridge. The possibility of decreasing complexes formation by solubilizing peptides in a dissociation mixture (containing glycine, urea, dithiothreitol and beta-mercaptoethanol), is discussed.