There is provided a method for plasmid DNA extraction to reproducibly yield relatively crude preparation which is suitable for transfection into mammalian cells. The inventors have determined that the high level of purification previously thought to be necessary in order to successfully allow transfection of the plasmid DNA into cells is not required. The inventors have developed a method of producing a transfectable plasmid preparation that can be performed on a large scale that avoids the use of specialized equipment and reagents.