The Complete Active Space (GAS) SCF method and multiconfigurational second-order perturbation theory (CASPT2) have been used in a theoretical analysis of the electronic spectra of glycine and N-acetylglycine. The calculations comprise a large number of singlet valence and Rydberg excited states. The electronic spectrum of glycine is dominated by excitations located at the carboxylic acid group. Two valence pi-->pi* states (named NV1’ and NV2’) have been computed at 8.10 and 10.20 eV with intensities 0.194 and 0.125, respectively. We found in glycine two weak valence n-->pi* states 5.65 and 6.51 eV above the ground state. One involves excitations from the lone pair orbital on the carboxylic oxygen. The second can be characterized as an intramolecular charge transfer stare from the amine terminal group to the peptide unit. A n-->sigma* excited state comprising excitations from the in-plane lone pair of the nitrogen is suggested to be responsible for a weak band around 8.6 eV. The spectrum of N-acetylglycine is shown to be composed of the superposition of the spectra of the peptide bend and the carboxylic acid group, the chromophores forming the system. We computed for N-acetylglycine the NV1 amide band at 6.76 eV, the NV1’ acid band at 8.55 eV, the NV2 band at 9.51 eV, and an intramolecular charge transfer state at 10.13 eV as the most intense features of the absorption spectrum. Based on these results and qualitative calculations on a simple dipeptidic system the most important features of the spectra of larger polypeptides are suggested to be composed of the following excitations : a weak band at 5.5 eV is caused by the n-->pi* excitation from the oxygen lone pairs, a band at 6.5 eV due to n-->pi* NV1 transitions localized at the peptide group, a band at 7.5 eV due to charge transfer states involving electronic transitions between neighboring peptide units, and a broad band at higher energies which is mainly composed of the second pi-->pi* NV2 valence state of the peptide group.