Laser desorption/Fourier-transform mass spectrometry (l.d./F t.m.s.) has been used to investigate the feasibility of desorbing nucleosides, oligosaccharides, and glycosides into the gas phase. Nucleosides were desorbed as (M -H)-ions or as (M + H)+ or more readily as alkali metal ion cationized species. Monosaccharides also could be desorbed as (M-H)but not di-or tri-saccharides. At higher laser irradiance, very abundant cationized oligosaccharides were observed. This was particularly true when the Nd:YAG laser was operated in a non-Q-switched mode to give a longer lasting laser pulse. Ions of non-reducing sugars cleaved at the glycosidic bond, but those of reducing sugars underwent ring cleavage reactions. Various glycosides including quercitrin, rutin, xanthorhamnin, digoxin, digitoxin, and erythromycin were also successfully desorbed as cationized species by using l.d./ F.t.m.s. Digoxin and digitoxin (M + Na)' ions fragment differently than the (M + H)' ions, presumably because the sodium ion is primarily affiliated with the sugar moiety whereas H+ is bound on the steroid portion of the molecule. This paper describes the utility of laser desorption/Fourier-transform mass spectrometry (1.dJF.t.m.s.) for investigating various biomolecules including saccharides, nucleosides, and glycosides. These molecules tend to exist as neutral species in the solid state, and the most efficient mechanism for vaporization/ionization appears to be thermal desorption and cationization (see below). In the accompanying paper, the precision or reproducibility of 1.dJF.t.m.s. is discussed in terms of various desorption mechanisms proposed in the literature. Laser desorption/mass spectrometry (1.dJm.s.) dates from 1963 [ 11, and the first application to organic salts was in 1970 [2] . Posthumus et al. [3] demonstrated that high-power lasers could be used to generate molecular ion species for several classes of biomolecules. Reviews of the work published until 1979 [4] and the experimental arrangements currently used [5] have appeared recently. Lasers, and particularly pulsed lasers, are attractive sources of energy for vaporizing solid molecular samples. They can be viewed as sources for rapid delivery of thermal energy. Fast heating is known to lead to preferential evaporation over thermal degradation [6, 71. The mass analyzer most often