Abstract: An automated mass spectrometric system which is capable of analyzing and identifying a wide variety of chemical compounds. A sample of an unknown compound, in liquid, solid or gaseous state, is introduced into the invented system. It may be a pure sample or a mixture of compounds. In either case, its mass spectrum is searched for selected peaks and an attempt is made to match such peaks to previously stored, characteristic spectra of one or more compounds in a predetermined family of compounds. Matching is on a probabilistic basis, reflecting the occurrence probabilities or uniqueness of the mass peaks found, and the accuracy with which the relative peak intensity pattern matches that of any of the compounds in the family of compounds sought. If one or more of the compounds in the family of compounds is identified as being present in the sample, its quantity is also determined automatically by the invention.