This facility represents a national resource of instrumentation and expertise in computerized double focusing high resolution mass spectrometry which is available to the bio-organic, biomedical and clinical research community for use in the characterization of microgram to nanogram quantities of biologically important compounds. Techniques of accurate mass measurement and elemental composition assignment are provided for use with a high resolution mass spectrometer operated in the electron impact mode and employing either direct probe or glass capillary gas chromatographic introduction of sample. Field desorption, collision-induced dissociation and linked scan techniques are also available for use with underivatized, polyfunctional, and chemically and/or thermally labile compounds. On-going collaborative projects include studies of steroid metabolism in hypermineralocorticoid hypertension, the investigation of drug metabolism and conjugation, metabolic diseases, the determination molecular structure of toxins, the study of covalently bound adducts formed between metabolically activated xenobiotics and cellular macromolecules, and structures of oligosaccharides.