This paper presents an investigation into two crucial aspects of microfluidic applications, namely hydrodynamic /electrokinetic focusing and switching. This study commences by modeling the hydrodynamic/electrokinetic focusing phenomenon theoretically using potential flow theory. A new theoretical model is applied to predict the width of the focused stream. The results predicted by the theoretical model are shown to be in reasonable agreement with the experimental data and numerical simulation results. The paper then proceeds to study the hydrodynamic and electrokinetic switching functions systematically using both experimental and theoretical approaches. A simple control model for 1×N electrokinetically pre-focused micro-flow switches is proposed. The study concludes by performing a systematic comparison of hydrodynamic and electrokinetic focusing/switching. The results of this study provide a useful methodology for the analysis of flow control in microfluidic devices.