Micromachined devices made of plastic have been used for fast electrophoretic separations using short separation distances and high electric field strengths. Unlike their glass counterparts, plastic chips can be manufactured economically and in high volume. Analysis can be performed in single channels, as shown for DNA sequencing mixtures, or in channel arrays as demonstrated for the analysis of ds DNA fragments. Compared to slab gel electrophoresis and capillary electrophoresis, separations are extremely fast with a time-scale under 20 minutes for a sequence analysis and under 2 minutes for fragment analysis. Confocal laser- induced fluorescence provides a sensitive means of detection.