Tandem mass spectrometry (ms/ms) is reviewed with illustrations of its applications drawn from the natural products area. The various types of ms/ms scans-daughter, parent, and neutral loss-are described together with their favorable effects on ms detection limits and speed of analysis. The applications of ms/ms in conjunction with desorption ionization for the identification of quaternary alkaloids are illustrated. Isomer identification including energy resolved forms of ms/ms, the use of negative ions, and aspects of fragmentation patterns in ms/ms are all presented. Applications of tandem mass spectrometry to mapping alkaloid distribution, detection of new trace alkaloids, and quantitative analysis are covered. © 1984, American Chemical Society. All rights reserved.