The authors have fabricated a microfluidic system for the control of DNA motion consisting of 400 or 900 nm wide Si channels covered by a bonded glass layer containing integrated dual electrodes. By applying an ac potential to an electrode pair on both sides of the channels, precise lateral positioning of DNA has been demonstrated for the first time. By modifying the amplitude or frequency of the ac potential applied to the electrode pairs, they control DNA motion within the channel, causing it to increase speed, decrease speed, reverse directions, or halt. The precise control of DNA average position within channels is expected to be an important step in the development of microfluidic single molecule analysis systems.