Many routine genomic-analysis assays rely on gel electrophoresis to perform size-selective fractionation of DNA fragments in the size range below 1 kb in length. Over the past decade, impressive progress has been made towards the development of microfabricated electrophoresis systems to conduct these assays in a microfluidic lab-on-a-chip format. Since these devices are inexpensive, require only nanolitre sample volumes, and do not rely on the availability of a pre-existing laboratory infrastructure, they are readily deployable in remote field locations for use in a variety of medical and biosensing applications. The design and construction of microfabricated electrophoresis devices poses a variety of challenges, including the need to achieve high-resolution separations over distances of a few centimetres or less, and the need to easily interface with additional microfluidic components to produce self-contained integrated DNA-analysis systems. In this paper, we review recent efforts to develop devices to satisfy these requirements and live up to the promise of fulfilling the growing need for inexpensive portable genomic-analysis equipment.