Gel electrophoresis is commonly used to separate DNA, but narrow capillaries or microchannels desired for hi h throughput efficient separations are difficult to fill with gels. We report here that a narrow capillary can be used to hydrodynamically separate a wide size range of DNA fragments in a single run without the need for gels, wall coatings, or an electric field. We also demonstrate that attractive separation is possible in a few minutes and that the separated DNA can be collected into individual fractions that remain viable for amplification via the polymerase chain reaction.