Electrospray ionization-mass spectrometry (ESI-MS) is a powerful tool for the characterization of intact proteins. However, complex samples require separation in order to obtain clear mass spectra and avoid matrix interaction; capillary electrophoresis (CE) has been shown to be a powerful separation technique for intact proteins. Herein, we present a method based on capillary zone electrophoretic (CZE) separation coupled online with mass spectrometric protein detection. While this approach is suitable for the separation and characterization of various intact proteins, the emphasis is placed on the separation of glycoforms of various and rather complex glycoproteins. The method has been successfully applied to the analysis of glycoproteins, e.g., erythropoietin, fetuin, and alpha-acid glycoprotein.