After a peptide or peptidomimetic sequence is optimized for ensuing drug development, non-radioactive labeling allows studying its biodistribution, cellular localization and receptor binding kinetics, among many other properties. Most frequently amide groups are acylated with visible, fluorogenic, or otherwise easily detectable acids though the amino terminus or lysine side-chains. The yield of conjugation depends upon the size and electron withdrawing effects of the label, and more importantly upon its hydrophobicity that determines the parameters of purification by reversed-phase chromatography. Covalent attachment of the label usually lowers the affinity of sequence minimized peptides to their biological targets that has to be carefully considered when assessing kinetic and thermodynamic constants. In biological environment, non-proteinogenic labels are expected to remain attached to the peptide backbone longer than natural amino acid linkages are cleaved by peptidases making identification of tissue and cellular localization sites complicated. Finally many labels themselves are ligands of natural targets or bind non-specifically to cell components. This presentation will highlight the pros and cons of non-radioactive peptide labeling focusing on drug development and using own examples from antibacterial, oncology and metabolic disease research in the past couple of decades.