If one has a purified stock of viruses obtained, for example, by banding in a buoyant density gradient, or even a relatively pure viral concentrate obtained by size fractionation, it is possible to release the DNA in a high molecular weight form suitable for some applications (e.g., pulsed-field gel electrophoresis [PFGE] for sizing or probing, or nucleic acid quantification\u00a0by fluorescence) relatively simply. This method involves exchanging the buffer in which the viruses are suspended with one containing EDTA and SDS, followed by heating. The method is similar to that described previously (Steward 2001), but with the optional addition of detergent to facilitate disintegration of the viral capsid.This is a protocol from:\u00a0Steward, G. F. and A. I. Culley. 2010. Chapter 16: Extraction and purification of nucleic acids from viruses.\u00a0Manual of Aquatic Viral Ecology. Waco, TX:American Society of Limnology and Oceanography. doi:10.4319\/mave.2010.978-0-9845591-0-7Please see the published manuscript for additional information.