For the first time, the standard Gibbs energies of the transfer of peptide anions from aqueous solution to nitrobenzene were determined with the help of electrochemical measurements. These systematic studies clearly show that the lipohilicity contributions of single amino acid residues to the overall lipohilicity of a peptide anion strongly depend on the position of the amino acid in the backbone of the peptide. Therefore, additive models to calculate the overall lipophilicity of a peptide cannot provide very precise data. The present study is a plea for the experimental establishment of a data set that takes into account the individual nature of an amino acid residue and its position in a peptide.