A selection of 58 specimens with a monoclonal component identified by immunoelectrophoresis and/or immunofixation was analyzed with the immunosubtraction procedure on the Paragon 2000 capillary electrophoresis system. The capillary system detected 93% of the paraproteins and, using immunosubtraction, correctly identified 91% of the paraproteins. Paraproteins that were detected by immunofixation and/or immunoelectrophoresis but not by capillary electrophoresis were also missed by agarose electrophoresis and cellulose acetate electrophoresis. Cellulose acetate electrophoresis was the least sensitive method for detection of paraproteins. Only 74% of the monoclonal components were detected by this technique, whereas 86% were revealed by agarose electrophoresis. In addition to monoclonal paraproteins, we also studied biclonal paraproteins and oligoclonal banding. Capillary electrophoresis and immunosubtraction correctly detected and identified three specimens containing biclonal paraproteins. In one specimen, capillary zone electrophoresis detected only one band, whereas agarose gel electrophoresis detected two bands. The sensitivity for detection and identification of oligoclonal banding by capillary electrophoresis was inferior to immunofixation.