Capillary isoelectric focusing (CIEF) is reviewed in this article with 64 references. Separation mechanism, manipulation of electroosmosis, mobilization methods, detectors and some problems associated with the determination of samples are discussed. Different methods for performing CIEF are evaluated. Non-cross-linked polyacrylamide coated capillary is recommended. As for untreated column, dynamical coating with cellulose polymers allows a residual electroosmotic flow to carry the focused zone to pass through the detector. Some applications, such as separation of transferrin isoform, human Hb variants, t-PA glycoform, are presented.