Abstract The ORD and CD spectra, in the uv region, of poly-S-benzyl-L-cysteine, poly-S-carbobenzoxy-L-cysteine and poly-O-carbobenzoxy-L-serine, in non-aqueous solution are presented. The first two polypeptides exhibit aromatic CD bands due to the phenyl chromophore, indicating specific orientations of their side chains in the β-conformation. The far-uv CD spectra in the non-aqueous medium reveal features that resemble closely those obtained in aqueous solutions and films. However, the ORD spectra in these two cases differ considerably, even in the sign of their rotations, emphasizing the role of the solvent. These data are expected to be of use in the interpretation of the spectra of globular proteins containing the β-structure, especially in their hydrophobic regions.