Two modified methods for measuring the ¿-potential and electroosmotic flow in capillaries for electrophoretic or electrochrmatographic separations are discussed. Streaming potential measurements with computer control and data acquisition can be used off-line for rapid screening of the behaviour of capillaries. To test the equipment, the variation of the ¿-potential with pH was performed and the characteristics of the system are discussed. Weighing measurements were performed on-line. The variation of the measurements with increased electric field strength are shown. For both methods the reproducibility and the accuracy are discussed.