The utility of surface-induced dissociation (SID) to probe the structure, energetics and fragmentation mechanisms of protonated peptides is discussed and demonstrated. High internal energy deposition provided by low-energy (eV range) ion-surface collisions yields extensive fragmentation of protonated peptides, allowing relatively uncomplicated and rapid sequence analysis of oligopeptides. SID of multiply protonated peptides is illustrated for peptides with molecular mass of up to approximately 5000 u. It is also illustrated that SID combined with electrospray ionization (ESI) provides a distinctive experimental technique to determine the energetics and mechanisms of peptide fragmentation. The relative position of ESI/SID fragmentation efficiency curves (plots of percentage fragmentation vs. laboratory collision energy) for peptides can be utilized to estimate relative energetics of peptide fragmentation and even to predict proton localization sites. The observed trends support the essential role of the mobile proton model in understanding peptide fragmentation by low-energy tandem mass spectrometry.