On the basis of the finding of two sets of coupling constants (8.8 Hz and 6.7 Hz) in the 270-MHz proton magnetic resonance spectra of linear Gramicidin in dimethylsulfoxide and the comparison of its infrared spectrum with those of known conformations of alternating poly(gamma-benzyl-D-glutamate--gamma-benzyl-L-glutamate), it is proposed that the antibiotic has an LD-ribbon structure.