Use of the dichromophoric CD assay for beta-turn formation in peptide sequences has been investigated. The assay involves the observation of Cotton effects in CD spectra, originating from the approach of N- and C-terminal aromatic chromophores in tetrapeptides. The approach of the chromophores was believed to be brought about by a beta-turn in the peptide structure. Our investigations were paralleled by NMR studies which revealed the presence of a previously unreported hydrogen bond in the beta-turn conformers, which appears to play a role in the generation of the observed Cotton effects. This suggests caution in the use of the CD technique alone as an assay for beta-turn conformers in peptides.