We investigated the influence of peptide size on the apparent loss of sequence during collision-induced dissociation (CID) of b ions using a group of peptides containing from between 4 and 10 residues. Although scrambling of sequence for b3+ generated from tetrapeptides is minimal, significant formation of nondirect sequence ions (i.e., ions for which scrambling has apparently occurred) was observed for all larger b ions included in the study.