The fragmentation of peptides and oligosaccharides in the gas phase was investigated by means of electrospray ionization Fourier transform ion cyclotron resonance (FTICR) mass spectrometry coupled with dissociation by a laser-cleavage infrared multiphoton dissociation (IRMPD) technique. In this technique, an IR free-electron laser is used as a tunable source of IR radiation to cause cleavage of the ionized samples introduced into the FTICR cell. The gas-phase IRMPD spectra of protonated peptides (substance P and angiotensin II) and two sodiated oligosaccharides (sialyl Lewis X and lacto-N-fucopentaose III) were obtained over the IR scan range of 5.7-9.5 Am. In the IRMPD spectra for the peptide, fragment ions are observed as y/b-type fragment ions in the range 5.7-7.5 Am, corresponding to cleavage of the backbone of the parent amino acid sequence, whereas the spectra of the oligosaccharides have major peaks in the range 8.4-9.5 Am, corresponding to photoproducts of the B/Y type.