Updated project metadata. Updated publication reference for PubMed record(s): 29900295. Blood as connective tissue potentially contain evidence of all processes occurring within the organism, at least in trace amounts. Because of their small size, peptides overcome cell membranes and epithelial barriers more freely than proteins. Among the peptides found in blood, there are both fragments of proteins secreted by various tissues and performing their function in plasma, as well as receptor ligands: hormones, cytokines, mediators of the cellular response. In addition, in minor amounts, there are disease peptide markers (for example, oncomarkers) and even foreign peptides related to pathogenic organisms and infection agents. To characterize the normal peptidome LC-MS/MS analysis was carried out of blood serum and plasma samples taken from 20 healthy donors on TripleTOF 5600+ mass-spectrometer. Sample preparation was carried out based on our previously developed method of peptide desorption from the surface of abundant blood plasma proteins followed by standard chromatographic steps.