Proton magnetic resonance and conformational energy calculations are presented for the cyclic peptide cyclo-(VPGVG)3 containing the pentamer repeat of elastin. The *H NMR spectrum of the molecule is obtained in methanol and the temperature dependence of the peptide NH protons are reported for this solvent over the range 0-60 °C. The observation of a pentamer spectrum, at all temperatures, demonstrates that the molecule has a threefold symmetry on the 220-MHz time scale. ABX analysis is done for the Gly CH2 spin systems and the 3J vicinal and 2J geminal coupling constants are derived. From the observed coupling constants, acceptable ranges of values for the torsion angles, ø, about N-Cα bonds are worked out. Reasonable ranges of values for torsion angles, ɇ, about the Cα-C bonds are gleaned from wire models built by using threefold symmetry and secondary structural constraints. By varying the backbone torsion angles within the ranges expected from coupling constants and from molecular models, it was possible to obtain a set of exactly threefold symmetric conformations. Conformational energy calculations are carried out, followed by detailed energy minimization. Six minimum energy structures are fully described. The torsion angles of three of these are consistent with NMR data. One of the structures is quite similar to the crystal structure of this molecule. © 1981, American Chemical Society. All rights reserved.