Presents various roles for mass spectrometry in the detection and characterization of microorganisms. Features GC-MS for clinical diagnosis of viral infection. Summarizes the status of detection of biological agents and of modifications in ribonucleic acids in microorganisms. Also describes electrospray, laser desorption, and tandem mass spectrometry for protein processing and modification in viruses. Includes discussion of membrane liposaccharide structures in pathogenic bacteria.