We present and demonstrate a novel technique for the purification of nucleic acids from biological samples using isotachophoresis (ITP). We demonstrate a simple and rapid method to achieve ITP-based extraction, preconcentration, and purification of DNA from nanoliter volumes of whole blood. We show that ITP purification yields genomic DNA samples which can be quantitated with fluorescence measurements and are immediately compatible with polymerase chain reaction (PCR) (e.g., a PCR-friendly solution free of significant inhibitors). We hypothesize ITP purification is applicable to processing of a wide range of complex biological samples.