This paper reports an improvement of the detectability in the capillary electrophoretic analysis of glycoproteins by using a sweeping technique based on the complexation between glycoproteins and borate ions: sweeping via borate complexation. In this technique, an anionic glycoprotein solution containing no borate ions is injected as a long plug into a capillary filled with a borate buffer. Due to the complexation between glycoproteins and borate ions, the analytes in a long sample zone are swept by borate ions to a narrow zone. When g1-acid glycoprotein dissolved in a phosphate buffer was injected into poly(vinyl pyrrolidone) coated capillary filled with 50 mM borate buffer (pH 10.0) for 120 s, the 30-40 fold increase in the sensitivity was achieved relative to conventional zone electrophoretic analysis. Furthermore, three glycoproteins could be separated with enhanced sensitivities under the sweeping via borate complexation condition. The enrichment efficiency was dependent on the sugar chain content of the glycoproteins. This indicated that the complexation of glycoproteins with borate ions played a crucial role in the sweeping via borate complexation technique.