Capillary electrophoresis-mass spectrometry (CE-MS) has proven to be useful for metabolomics studies. Charged metabolites are first separated by CE based on charge and size and are subsequently selectively detected using MS. The major advantages of CE-MS are its high resolution and the fact that almost any charged species can be analyzed by two methods, both cationic and anionic. This technique can readily be applied to various types of biological samples originating from bacteria, plants, mammals, and body fluids. This chapter highlights detailed practical procedures for using this technology.