A 17-residue O-linked glycopeptide model incorporating a central alpha-mannosyl serine residue, and its unglycosylated analog both demonstrate substantial helicity in water. The peptide sequence was derived from previous studies in which differences in overall helicity as a function of single amino acid substitutions were measured by circular dichroism (CD). The helical content was predicted by molecular modeling, and confirmed by CD and NMR. Moreover, the glycopeptide retained its helicity in the presence of SDS micelles, whereas the native peptide lost secondary structure in the presence of micelles. The inference is that the peptide sequence is a more important helix determinant than glycosylation per se.